Commit Graph

89 Commits

Author SHA1 Message Date
Dan Williams
304ec1b050 x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
Quoting Linus:

    I do think that it would be a good idea to very expressly document
    the fact that it's not that the user access itself is unsafe. I do
    agree that things like "get_user()" want to be protected, but not
    because of any direct bugs or problems with get_user() and friends,
    but simply because get_user() is an excellent source of a pointer
    that is obviously controlled from a potentially attacking user
    space. So it's a prime candidate for then finding _subsequent_
    accesses that can then be used to perturb the cache.

__uaccess_begin_nospec() covers __get_user() and copy_from_iter() where the
limit check is far away from the user pointer de-reference. In those cases
a barrier_nospec() prevents speculation with a potential pointer to
privileged memory. uaccess_try_nospec covers get_user_try.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727416953.33451.10508284228526170604.stgit@dwillia2-desk3.amr.corp.intel.com
2018-01-30 21:54:31 +01:00
Dan Williams
b3bbfb3fb5 x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
For __get_user() paths, do not allow the kernel to speculate on the value
of a user controlled pointer. In addition to the 'stac' instruction for
Supervisor Mode Access Protection (SMAP), a barrier_nospec() causes the
access_ok() result to resolve in the pipeline before the CPU might take any
speculative action on the pointer value. Given the cost of 'stac' the
speculation barrier is placed after 'stac' to hopefully overlap the cost of
disabling SMAP with the cost of flushing the instruction pipeline.

Since __get_user is a major kernel interface that deals with user
controlled pointers, the __uaccess_begin_nospec() mechanism will prevent
speculative execution past an access_ok() permission check. While
speculative execution past access_ok() is not enough to lead to a kernel
memory leak, it is a necessary precondition.

To be clear, __uaccess_begin_nospec() is addressing a class of potential
problems near __get_user() usages.

Note, that while the barrier_nospec() in __uaccess_begin_nospec() is used
to protect __get_user(), pointer masking similar to array_index_nospec()
will be used for get_user() since it incorporates a bounds check near the
usage.

uaccess_try_nospec provides the same mechanism for get_user_try.

No functional changes.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andi Kleen <ak@linux.intel.com>
Suggested-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727415922.33451.5796614273104346583.stgit@dwillia2-desk3.amr.corp.intel.com
2018-01-30 21:54:30 +01:00
Greg Kroah-Hartman
b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
Ville Syrjälä
5ac751d9e6 x86: Don't cast away the __user in __get_user_asm_u64()
Don't cast away the __user in __get_user_asm_u64() on x86-32.
Prevents sparse getting upset.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20170912164000.13745-1-ville.syrjala@linux.intel.com
2017-09-25 09:36:16 +02:00
Josh Poimboeuf
f5caf621ee x86/asm: Fix inline asm call constraints for Clang
For inline asm statements which have a CALL instruction, we list the
stack pointer as a constraint to convince GCC to ensure the frame
pointer is set up first:

  static inline void foo()
  {
	register void *__sp asm(_ASM_SP);
	asm("call bar" : "+r" (__sp))
  }

Unfortunately, that pattern causes Clang to corrupt the stack pointer.

The fix is easy: convert the stack pointer register variable to a global
variable.

It should be noted that the end result is different based on the GCC
version.  With GCC 6.4, this patch has exactly the same result as
before:

	defconfig	defconfig-nofp	distro		distro-nofp
 before	9820389		9491555		8816046		8516940
 after	9820389		9491555		8816046		8516940

With GCC 7.2, however, GCC's behavior has changed.  It now changes its
behavior based on the conversion of the register variable to a global.
That somehow convinces it to *always* set up the frame pointer before
inserting *any* inline asm.  (Therefore, listing the variable as an
output constraint is a no-op and is no longer necessary.)  It's a bit
overkill, but the performance impact should be negligible.  And in fact,
there's a nice improvement with frame pointers disabled:

	defconfig	defconfig-nofp	distro		distro-nofp
 before	9796316		9468236		9076191		8790305
 after	9796957		9464267		9076381		8785949

So in summary, while listing the stack pointer as an output constraint
is no longer necessary for newer versions of GCC, it's still needed for
older versions.

Suggested-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3db862e970c432ae823cf515c52b54fec8270e0e.1505942196.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-23 15:06:20 +02:00
Linus Torvalds
6c51e67b64 Merge branch 'x86-syscall-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull syscall updates from Ingo Molnar:
 "Improve the security of set_fs(): we now check the address limit on a
  number of key platforms (x86, arm, arm64) before returning to
  user-space - without adding overhead to the typical system call fast
  path"

* 'x86-syscall-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  arm64/syscalls: Check address limit on user-mode return
  arm/syscalls: Check address limit on user-mode return
  x86/syscalls: Check address limit on user-mode return
2017-09-04 11:18:17 -07:00
Linus Torvalds
89cbec71fe Merge branch 'work.uaccess-unaligned' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull uacess-unaligned removal from Al Viro:
 "That stuff had just one user, and an exotic one, at that - binfmt_flat
  on arm and m68k"

* 'work.uaccess-unaligned' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  kill {__,}{get,put}_user_unaligned()
  binfmt_flat: flat_{get,put}_addr_from_rp() should be able to fail
2017-07-15 11:17:52 -07:00
Thomas Garnier
5ea0727b16 x86/syscalls: Check address limit on user-mode return
Ensure the address limit is a user-mode segment before returning to
user-mode. Otherwise a process can corrupt kernel-mode memory and elevate
privileges [1].

The set_fs function sets the TIF_SETFS flag to force a slow path on
return. In the slow path, the address limit is checked to be USER_DS if
needed.

The addr_limit_user_check function is added as a cross-architecture
function to check the address limit.

[1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990

Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: kernel-hardening@lists.openwall.com
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Pratyush Anand <panand@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Will Drewry <wad@chromium.org>
Cc: linux-api@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170615011203.144108-1-thgarnie@google.com
2017-07-08 14:05:32 +02:00
Linus Torvalds
dc502142b6 Merge branch 'uaccess.strlen' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull user access str* updates from Al Viro:
 "uaccess str...() dead code removal"

* 'uaccess.strlen' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  s390 keyboard.c: don't open-code strndup_user()
  mips: get rid of unused __strnlen_user()
  get rid of unused __strncpy_from_user() instances
  kill strlen_user()
2017-07-06 22:07:44 -07:00
Al Viro
3170d8d226 kill {__,}{get,put}_user_unaligned()
no users left

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-07-03 18:44:22 -04:00
Linus Torvalds
33c9e97290 x86: fix 32-bit case of __get_user_asm_u64()
The code to fetch a 64-bit value from user space was entirely buggered,
and has been since the code was merged in early 2016 in commit
b2f680380d ("x86/mm/32: Add support for 64-bit __get_user() on 32-bit
kernels").

Happily the buggered routine is almost certainly entirely unused, since
the normal way to access user space memory is just with the non-inlined
"get_user()", and the inlined version didn't even historically exist.

The normal "get_user()" case is handled by external hand-written asm in
arch/x86/lib/getuser.S that doesn't have either of these issues.

There were two independent bugs in __get_user_asm_u64():

 - it still did the STAC/CLAC user space access marking, even though
   that is now done by the wrapper macros, see commit 11f1a4b975
   ("x86: reorganize SMAP handling in user space accesses").

   This didn't result in a semantic error, it just means that the
   inlined optimized version was hugely less efficient than the
   allegedly slower standard version, since the CLAC/STAC overhead is
   quite high on modern Intel CPU's.

 - the double register %eax/%edx was marked as an output, but the %eax
   part of it was touched early in the asm, and could thus clobber other
   inputs to the asm that gcc didn't expect it to touch.

   In particular, that meant that the generated code could look like
   this:

        mov    (%eax),%eax
        mov    0x4(%eax),%edx

   where the load of %edx obviously was _supposed_ to be from the 32-bit
   word that followed the source of %eax, but because %eax was
   overwritten by the first instruction, the source of %edx was
   basically random garbage.

The fixes are trivial: remove the extraneous STAC/CLAC entries, and mark
the 64-bit output as early-clobber to let gcc know that no inputs should
alias with the output register.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@kernel.org   # v4.8+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-21 18:26:54 -07:00
Linus Torvalds
334a023ee5 Clean up x86 unsafe_get/put_user() type handling
Al noticed that unsafe_put_user() had type problems, and fixed them in
commit a7cc722fff ("fix unsafe_put_user()"), which made me look more
at those functions.

It turns out that unsafe_get_user() had a type issue too: it limited the
largest size of the type it could handle to "unsigned long".  Which is
fine with the current users, but doesn't match our existing normal
get_user() semantics, which can also handle "u64" even when that does
not fit in a long.

While at it, also clean up the type cast in unsafe_put_user().  We
actually want to just make it an assignment to the expected type of the
pointer, because we actually do want warnings from types that don't
convert silently.  And it makes the code more readable by not having
that one very long and complex line.

[ This patch might become stable material if we ever end up back-porting
  any new users of the unsafe uaccess code, but as things stand now this
  doesn't matter for any current existing uses. ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-21 15:25:46 -07:00
Al Viro
a7cc722fff fix unsafe_put_user()
__put_user_size() relies upon its first argument having the same type as what
the second one points to; the only other user makes sure of that and
unsafe_put_user() should do the same.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-05-21 13:09:57 -04:00
Al Viro
8298525839 kill strlen_user()
no callers, no consistent semantics, no sane way to use it...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-05-15 23:40:22 -04:00
Al Viro
beba3a20bf x86: switch to RAW_COPY_USER
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-29 12:06:28 -04:00
Al Viro
122b05ddf5 amd64: get rid of zeroing
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-28 18:24:04 -04:00
Al Viro
af1d5b37d6 uaccess: drop duplicate includes from asm/uaccess.h
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-05 21:57:49 -05:00
Al Viro
5e6039d8a3 uaccess: move VERIFY_{READ,WRITE} definitions to linux/uaccess.h
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-05 20:40:25 -05:00
Peter Zijlstra
7c4788950b x86/uaccess, sched/preempt: Verify access_ok() context
I recently encountered wreckage because access_ok() was used where it
should not be, add an explicit WARN when access_ok() is used wrongly.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-12-06 10:32:40 +01:00
Al Viro
45caf47007 x86: separate extable.h, switch sections.h to it
drivers/platform/x86/dell-smo8800.c is touched due to the following obscenity:
drivers/platform/x86/dell-smo8800.c ->
	linux/interrupt.h ->
		linux/hardirq.h ->
			asm/hardirq.h ->
				linux/irq.h ->
					asm/hw_irq.h ->
						asm/sections.h ->
							asm/uaccess.h
is the only chain of includes pulling asm/uaccess.h there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-09-27 21:15:23 -04:00
Al Viro
1c109fabbd fix minor infoleak in get_user_ex()
get_user_ex(x, ptr) should zero x on failure.  It's not a lot of a leak
(at most we are leaking uninitialized 64bit value off the kernel stack,
and in a fairly constrained situation, at that), but the fix is trivial,
so...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[ This sat in different branch from the uaccess fixes since mid-August ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-09-15 12:54:04 -07:00
Kees Cook
e6971009a9 x86/uaccess: force copy_*_user() to be inlined
As already done with __copy_*_user(), mark copy_*_user() as __always_inline.
Without this, the checks for things like __builtin_const_p() won't work
consistently in either hardened usercopy nor the recent adjustments for
detecting usercopy overflows at compile time.

The change in kernel text size is detectable, but very small:

 text      data     bss     dec      hex     filename
12118735  5768608 14229504 32116847 1ea106f vmlinux.before
12120207  5768608 14229504 32118319 1ea162f vmlinux.after

Signed-off-by: Kees Cook <keescook@chromium.org>
2016-09-06 12:16:42 -07:00
Josh Poimboeuf
0d025d271e mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
There are three usercopy warnings which are currently being silenced for
gcc 4.6 and newer:

1) "copy_from_user() buffer size is too small" compile warning/error

   This is a static warning which happens when object size and copy size
   are both const, and copy size > object size.  I didn't see any false
   positives for this one.  So the function warning attribute seems to
   be working fine here.

   Note this scenario is always a bug and so I think it should be
   changed to *always* be an error, regardless of
   CONFIG_DEBUG_STRICT_USER_COPY_CHECKS.

2) "copy_from_user() buffer size is not provably correct" compile warning

   This is another static warning which happens when I enable
   __compiletime_object_size() for new compilers (and
   CONFIG_DEBUG_STRICT_USER_COPY_CHECKS).  It happens when object size
   is const, but copy size is *not*.  In this case there's no way to
   compare the two at build time, so it gives the warning.  (Note the
   warning is a byproduct of the fact that gcc has no way of knowing
   whether the overflow function will be called, so the call isn't dead
   code and the warning attribute is activated.)

   So this warning seems to only indicate "this is an unusual pattern,
   maybe you should check it out" rather than "this is a bug".

   I get 102(!) of these warnings with allyesconfig and the
   __compiletime_object_size() gcc check removed.  I don't know if there
   are any real bugs hiding in there, but from looking at a small
   sample, I didn't see any.  According to Kees, it does sometimes find
   real bugs.  But the false positive rate seems high.

3) "Buffer overflow detected" runtime warning

   This is a runtime warning where object size is const, and copy size >
   object size.

All three warnings (both static and runtime) were completely disabled
for gcc 4.6 with the following commit:

  2fb0815c9e ("gcc4: disable __compiletime_object_size for GCC 4.6+")

That commit mistakenly assumed that the false positives were caused by a
gcc bug in __compiletime_object_size().  But in fact,
__compiletime_object_size() seems to be working fine.  The false
positives were instead triggered by #2 above.  (Though I don't have an
explanation for why the warnings supposedly only started showing up in
gcc 4.6.)

So remove warning #2 to get rid of all the false positives, and re-enable
warnings #1 and #3 by reverting the above commit.

Furthermore, since #1 is a real bug which is detected at compile time,
upgrade it to always be an error.

Having done all that, CONFIG_DEBUG_STRICT_USER_COPY_CHECKS is no longer
needed.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-30 10:10:21 -07:00
Linus Torvalds
1eccfa090e Implements HARDENED_USERCOPY verification of copy_to_user/copy_from_user
bounds checking for most architectures on SLAB and SLUB.
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Merge tag 'usercopy-v4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull usercopy protection from Kees Cook:
 "Tbhis implements HARDENED_USERCOPY verification of copy_to_user and
  copy_from_user bounds checking for most architectures on SLAB and
  SLUB"

* tag 'usercopy-v4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  mm: SLUB hardened usercopy support
  mm: SLAB hardened usercopy support
  s390/uaccess: Enable hardened usercopy
  sparc/uaccess: Enable hardened usercopy
  powerpc/uaccess: Enable hardened usercopy
  ia64/uaccess: Enable hardened usercopy
  arm64/uaccess: Enable hardened usercopy
  ARM: uaccess: Enable hardened usercopy
  x86/uaccess: Enable hardened usercopy
  mm: Hardened usercopy
  mm: Implement stack frame object validation
  mm: Add is_migrate_cma_page
2016-08-08 14:48:14 -07:00
Linus Torvalds
1bd4403d86 unsafe_[get|put]_user: change interface to use a error target label
When I initially added the unsafe_[get|put]_user() helpers in commit
5b24a7a2aa ("Add 'unsafe' user access functions for batched
accesses"), I made the mistake of modeling the interface on our
traditional __[get|put]_user() functions, which return zero on success,
or -EFAULT on failure.

That interface is fairly easy to use, but it's actually fairly nasty for
good code generation, since it essentially forces the caller to check
the error value for each access.

In particular, since the error handling is already internally
implemented with an exception handler, and we already use "asm goto" for
various other things, we could fairly easily make the error cases just
jump directly to an error label instead, and avoid the need for explicit
checking after each operation.

So switch the interface to pass in an error label, rather than checking
the error value in the caller.  Best do it now before we start growing
more users (the signal handling code in particular would be a good place
to use the new interface).

So rather than

	if (unsafe_get_user(x, ptr))
		... handle error ..

the interface is now

	unsafe_get_user(x, ptr, label);

where an error during the user mode fetch will now just cause a jump to
'label' in the caller.

Right now the actual _implementation_ of this all still ends up being a
"if (err) goto label", and does not take advantage of any exception
label tricks, but for "unsafe_put_user()" in particular it should be
fairly straightforward to convert to using the exception table model.

Note that "unsafe_get_user()" is much harder to convert to a clever
exception table model, because current versions of gcc do not allow the
use of "asm goto" (for the exception) with output values (for the actual
value to be fetched).  But that is hopefully not a limitation in the
long term.

[ Also note that it might be a good idea to switch unsafe_get_user() to
  actually _return_ the value it fetches from user space, but this
  commit only changes the error handling semantics ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-08 13:02:01 -07:00
Kees Cook
5b710f34e1 x86/uaccess: Enable hardened usercopy
Enables CONFIG_HARDENED_USERCOPY checks on x86. This is done both in
copy_*_user() and __copy_*_user() because copy_*_user() actually calls
down to _copy_*_user() and not __copy_*_user().

Based on code from PaX and grsecurity.

Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
2016-07-26 14:41:48 -07:00
Andy Lutomirski
13d4ea097d x86/uaccess: Move thread_info::addr_limit to thread_struct
struct thread_info is a legacy mess.  To prepare for its partial removal,
move thread_info::addr_limit out.

As an added benefit, this way is simpler.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/15bee834d09402b47ac86f2feccdf6529f9bc5b0.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-15 10:26:30 +02:00
Andy Lutomirski
dfa9a942fd x86/uaccess: Move thread_info::uaccess_err and thread_info::sig_on_uaccess_err to thread_struct
struct thread_info is a legacy mess.  To prepare for its partial removal,
move the uaccess control fields out -- they're straightforward.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d0ac4d01c8e4d4d756264604e47445d5acc7900e.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-15 10:26:28 +02:00
Ingo Molnar
946e0f6ffc Linux 4.7-rc6
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Merge tag 'v4.7-rc6' into x86/mm, to merge fixes before applying new changes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-08 11:51:28 +02:00
Andrey Ryabinin
1771c6e1a5 x86/kasan: instrument user memory access API
Exchange between user and kernel memory is coded in assembly language.
Which means that such accesses won't be spotted by KASAN as a compiler
instruments only C code.

Add explicit KASAN checks to user memory access API to ensure that
userspace writes to (or reads from) a valid kernel memory.

Note: Unlike others strncpy_from_user() is written mostly in C and KASAN
sees memory accesses in it.  However, it makes sense to add explicit
check for all @count bytes that *potentially* could be written to the
kernel.

[aryabinin@virtuozzo.com: move kasan check under the condition]
  Link: http://lkml.kernel.org/r/1462869209-21096-1-git-send-email-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/1462538722-1574-4-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20 17:58:30 -07:00
Linus Torvalds
168f1a7163 Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm updates from Ingo Molnar:
 "The main changes in this cycle were:

   - MSR access API fixes and enhancements (Andy Lutomirski)

   - early exception handling improvements (Andy Lutomirski)

   - user-space FS/GS prctl usage fixes and improvements (Andy
     Lutomirski)

   - Remove the cpu_has_*() APIs and replace them with equivalents
     (Borislav Petkov)

   - task switch micro-optimization (Brian Gerst)

   - 32-bit entry code simplification (Denys Vlasenko)

   - enhance PAT handling in enumated CPUs (Toshi Kani)

  ... and lots of other cleanups/fixlets"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/arch_prctl/64: Restore accidentally removed put_cpu() in ARCH_SET_GS
  x86/entry/32: Remove asmlinkage_protect()
  x86/entry/32: Remove GET_THREAD_INFO() from entry code
  x86/entry, sched/x86: Don't save/restore EFLAGS on task switch
  x86/asm/entry/32: Simplify pushes of zeroed pt_regs->REGs
  selftests/x86/ldt_gdt: Test set_thread_area() deletion of an active segment
  x86/tls: Synchronize segment registers in set_thread_area()
  x86/asm/64: Rename thread_struct's fs and gs to fsbase and gsbase
  x86/arch_prctl/64: Remove FSBASE/GSBASE < 4G optimization
  x86/segments/64: When load_gs_index fails, clear the base
  x86/segments/64: When loadsegment(fs, ...) fails, clear the base
  x86/asm: Make asm/alternative.h safe from assembly
  x86/asm: Stop depending on ptrace.h in alternative.h
  x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
  x86/asm: Make sure verify_cpu() has a good stack
  x86/extable: Add a comment about early exception handlers
  x86/msr: Set the return value to zero when native_rdmsr_safe() fails
  x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y
  x86/paravirt: Add paravirt_{read,write}_msr()
  x86/msr: Carry on after a non-"safe" MSR access fails
  ...
2016-05-16 15:15:17 -07:00
Mathias Krause
50c73890d3 x86/extable: ensure entries are swapped completely when sorting
The x86 exception table sorting was changed in commit 29934b0fb8
("x86/extable: use generic search and sort routines") to use the arch
independent code in lib/extable.c.  However, the patch was mangled
somehow on its way into the kernel from the last version posted at [1].
The committed version kind of attempted to incorporate the changes of
commit 548acf1923 ("x86/mm: Expand the exception table logic to allow
new handling options") as in _completely_ _ignoring_ the x86 specific
'handler' member of struct exception_table_entry.  This effectively
broke the sorting as entries will only partly be swapped now.

Fortunately, the x86 Kconfig selects BUILDTIME_EXTABLE_SORT, so the
exception table doesn't need to be sorted at runtime. However, in case
that ever changes, we better not break the exception table sorting just
because of that.

[ Ard Biesheuvel points out that BUILDTIME_EXTABLE_SORT applies to the
  core image only, but we still rely on the sorting routines for modules
  in that case - Linus ]

Fix this by providing a swap_ex_entry_fixup() macro that takes care of
the 'handler' member.

[1] https://lkml.org/lkml/2016/1/27/232

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Fixes: 29934b0fb8 ("x86/extable: use generic search and sort routines")
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-11 11:17:47 -07:00
Mathias Krause
67d7a982ba x86/extable: Ensure entries are swapped completely when sorting
The x86 exception table sorting was changed in this recent commit:

  29934b0fb8 ("x86/extable: use generic search and sort routines")

... to use the arch independent code in lib/extable.c. However, the
patch was mangled somehow on its way into the kernel from the last
version posted at:

  https://lkml.org/lkml/2016/1/27/232

The committed version kind of attempted to incorporate the changes of
contemporary commit done in the x86 tree:

  548acf1923 ("x86/mm: Expand the exception table logic to allow new handling options")

... as in _completely_ _ignoring_ the x86 specific 'handler' member of
struct exception_table_entry. This effectively broke the sorting as
entries will only be partly swapped now.

Fortunately, the x86 Kconfig selects BUILDTIME_EXTABLE_SORT, so the
exception table doesn't need to be sorted at runtime. However, in case
that ever changes, we better not break the exception table sorting just
because of that.

Fix this by providing a swap_ex_entry_fixup() macro that takes care of
the 'handler' member.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1462914422-2911-1-git-send-email-minipli@googlemail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-05-11 11:14:06 +02:00
Benjamin LaHaise
b2f680380d x86/mm/32: Add support for 64-bit __get_user() on 32-bit kernels
The existing __get_user() implementation does not support fetching
64-bit values on 32-bit x86.  Implement this in a way that does not
generate any incorrect warnings as cautioned by Russell King.

Test code available at:

  http://www.kvack.org/~bcrl/x86_32-get_user.tar .

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 13:01:03 +02:00
Andy Lutomirski
0e861fbb5b x86/head: Move early exception panic code into early_fixup_exception()
This removes a bunch of assembly and adds some C code instead.  It
changes the actual printouts on both 32-bit and 64-bit kernels, but
they still seem okay.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/4085070316fc3ab29538d3fcfe282648d1d4ee2e.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 11:37:44 +02:00
Andy Lutomirski
7bbcdb1ca4 x86/head: Pass a real pt_regs and trapnr to early_fixup_exception()
early_fixup_exception() is limited by the fact that it doesn't have a
real struct pt_regs.  Change both the 32-bit and 64-bit asm and the
C code to pass and accept a real pt_regs.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/e3fb680fcfd5e23e38237e8328b64a25cc121d37.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 11:37:44 +02:00
Ard Biesheuvel
29934b0fb8 x86/extable: use generic search and sort routines
Replace the arch specific versions of search_extable() and
sort_extable() with calls to the generic ones, which now support
relative exception tables as well.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-22 15:36:02 -07:00
Ingo Molnar
319e305ca4 Merge branch 'ras/core' into core/objtool, to pick up the new exception table format
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-25 09:01:09 +01:00
Chris J Arges
f05058c4d6 x86/uaccess: Add stack frame output operand in get_user() inline asm
Numerous 'call without frame pointer save/setup' warnings are introduced
by stacktool because of functions using the get_user() macro. Bad stack
traces could occur due to lack of or misplacement of stack frame setup
code.

This patch forces a stack frame to be created before the inline asm code
if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an
output operand for the get_user() inline assembly statement.

Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/bc85501f221ee512670797c7f110022e64b12c81.1453405861.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-24 08:35:43 +01:00
Tony Luck
548acf1923 x86/mm: Expand the exception table logic to allow new handling options
Huge amounts of help from  Andy Lutomirski and Borislav Petkov to
produce this. Andy provided the inspiration to add classes to the
exception table with a clever bit-squeezing trick, Boris pointed
out how much cleaner it would all be if we just had a new field.

Linus Torvalds blessed the expansion with:

  ' I'd rather not be clever in order to save just a tiny amount of space
    in the exception table, which isn't really criticial for anybody. '

The third field is another relative function pointer, this one to a
handler that executes the actions.

We start out with three handlers:

 1: Legacy - just jumps the to fixup IP
 2: Fault - provide the trap number in %ax to the fixup code
 3: Cleaned up legacy for the uaccess error hack

Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f6af78fcbd348cf4939875cfda9c19689b5e50b8.1455732970.git.tony.luck@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-18 09:21:46 +01:00
Linus Torvalds
404a47410c Merge branch 'uaccess' (batched user access infrastructure)
Expose an interface to allow users to mark several accesses together as
being user space accesses, allowing batching of the surrounding user
space access markers (SMAP on x86, PAN on arm64, domain register
switching on arm).

This is currently only used for the user string lenth and copying
functions, where the SMAP overhead on x86 drowned the actual user
accesses (only noticeable on newer microarchitectures that support SMAP
in the first place, of course).

* user access batching branch:
  Use the new batched user accesses in generic user string handling
  Add 'unsafe' user access functions for batched accesses
  x86: reorganize SMAP handling in user space accesses
2016-01-21 13:02:41 -08:00
Linus Torvalds
5b24a7a2aa Add 'unsafe' user access functions for batched accesses
The naming is meant to discourage random use: the helper functions are
not really any more "unsafe" than the traditional double-underscore
functions (which need the address range checking), but they do need even
more infrastructure around them, and should not be used willy-nilly.

In addition to checking the access range, these user access functions
require that you wrap the user access with a "user_acess_{begin,end}()"
around it.

That allows architectures that implement kernel user access control
(x86: SMAP, arm64: PAN) to do the user access control in the wrapping
user_access_begin/end part, and then batch up the actual user space
accesses using the new interfaces.

The main (and hopefully only) use for these are for core generic access
helpers, initially just the generic user string functions
(strnlen_user() and strncpy_from_user()).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-12-17 09:57:27 -08:00
Linus Torvalds
11f1a4b975 x86: reorganize SMAP handling in user space accesses
This reorganizes how we do the stac/clac instructions in the user access
code.  Instead of adding the instructions directly to the same inline
asm that does the actual user level access and exception handling, add
them at a higher level.

This is mainly preparation for the next step, where we will expose an
interface to allow users to mark several accesses together as being user
space accesses, but it does already clean up some code:

 - the inlined trivial cases of copy_in_user() now do stac/clac just
   once over the accesses: they used to do one pair around the user
   space read, and another pair around the write-back.

 - the {get,put}_user_ex() macros that are used with the catch/try
   handling don't do any stac/clac at all, because that happens in the
   try/catch surrounding them.

Other than those two cleanups that happened naturally from the
re-organization, this should not make any difference. Yet.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-12-17 09:45:09 -08:00
Andi Kleen
10013ebb5d x86: Add an inlined __copy_from_user_nmi() variant
Add a inlined __ variant of copy_from_user_nmi. The inlined variant allows
the user to:

 - batch the access_ok() check for multiple accesses

 - avoid having a pagefault_disable/enable() on every access if the
   caller already ensures disabled page faults due to its context.

 - get all the optimizations in copy_*_user() for small constant sized
   transfers

It is just a define to __copy_from_user_inatomic().

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1445551641-13379-1-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:58:24 +01:00
Andy Lutomirski
7e0f51cb44 x86/uaccess: Add unlikely() to __chk_range_not_ok() failure paths
This should improve code quality a bit. It also shrinks the kernel text:

 Before:
       text     data      bss       dec    filename
   21828379  5194760  1277952  28301091    vmlinux

 After:
       text     data      bss       dec    filename
   21827997  5194760  1277952  28300709    vmlinux

... by 382 bytes.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/f427b8002d932e5deab9055e0074bb4e7e80ee39.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-07 11:34:06 +02:00
Andy Lutomirski
a76cf66e94 x86/uaccess: Tell the compiler that uaccess is unlikely to fault
GCC doesn't realize that get_user(), put_user(), and their __
variants are unlikely to fail.  Tell it.

I noticed this while playing with the C entry code.

 Before:
       text     data      bss       dec    filename
   21828763  5194760  1277952  28301475    vmlinux.baseline

 After:
      text      data      bss       dec    filename
   21828379  5194760  1277952  28301091    vmlinux.new

The generated code shrunk by 384 bytes.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/dc37bed7024319c3004d950d57151fca6aeacf97.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-07 11:34:06 +02:00
David Hildenbrand
b3c395ef55 mm/uaccess, mm/fault: Clarify that uaccess may only sleep if pagefaults are enabled
In general, non-atomic variants of user access functions must not sleep
if pagefaults are disabled.

Let's update all relevant comments in uaccess code. This also reflects
the might_sleep() checks in might_fault().

Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: benh@kernel.crashing.org
Cc: bigeasy@linutronix.de
Cc: borntraeger@de.ibm.com
Cc: daniel.vetter@intel.com
Cc: heiko.carstens@de.ibm.com
Cc: herbert@gondor.apana.org.au
Cc: hocko@suse.cz
Cc: hughd@google.com
Cc: mst@redhat.com
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: schwidefsky@de.ibm.com
Cc: yang.shi@windriver.com
Link: http://lkml.kernel.org/r/1431359540-32227-4-git-send-email-dahi@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-19 08:39:14 +02:00
Michael S. Tsirkin
e182c570e9 x86/uaccess: fix sparse errors
virtio wants to read bitwise types from userspace using get_user.  At the
moment this triggers sparse errors, since the value is passed through an
integer.

Fix that up using __force.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
2015-01-13 15:22:59 +02:00
Linus Torvalds
c9cdd9a6ae Merge branch 'x86/mpx' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cpufeature and mpx updates from Peter Anvin:
 "This includes the basic infrastructure for MPX (Memory Protection
  Extensions) support, but does not include MPX support itself.  It is,
  however, a prerequisite for KVM support for MPX, which I believe will
  be pushed later this merge window by the KVM team.

  This includes moving the functionality in
  futex_atomic_cmpxchg_inatomic() into a new function in uaccess.h so it
  can be reused - this will be used by the final MPX patches.

  The actual MPX functionality (map management and so on) will be pushed
  in a future merge window, when ready"

* 'x86/mpx' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/intel/mpx: Remove unused LWP structure
  x86, mpx: Add MPX related opcodes to the x86 opcode map
  x86: replace futex_atomic_cmpxchg_inatomic() with user_atomic_cmpxchg_inatomic
  x86: add user_atomic_cmpxchg_inatomic at uaccess.h
  x86, xsave: Support eager-only xsave features, add MPX support
  x86, cpufeature: Define the Intel MPX feature flag
2014-01-20 14:46:32 -08:00
H. Peter Anvin
a740576a4a x86: Slightly tweak the access_ok() C variant for better code
gcc can under very specific circumstances realize that the code
sequence:

	foo += bar;
	if (foo < bar) ...

... is equivalent to a carry out from the addition.  Tweak the
implementation of access_ok() (specifically __chk_range_not_ok()) to
make it more likely that gcc will make that connection.  It isn't
fool-proof (sometimes gcc seems to think it can make better code with
lea, and ends up with a second comparison), still, but it seems to be
able to connect the two more frequently this way.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/CA%2B55aFzPBdbfKovMT8Edr4SmE2_=%2BOKJFac9XW2awegogTkVTA@mail.gmail.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2013-12-27 17:02:53 -08:00