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00c42373d3
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Linus Torvalds 00c42373d3 x86-64: add warning for non-canonical user access address dereferences 
This adds a warning (once) for any kernel dereference that has a user
exception handler, but accesses a non-canonical address.  It basically
is a simpler - and more limited - version of commit 9da3f2b740
("x86/fault: BUG() when uaccess helpers fault on kernel addresses") that
got reverted.

Note that unlike that original commit, this only causes a warning,
because there are real situations where we currently can do this
(notably speculative argument fetching for uprobes etc).  Also, unlike
that original commit, this _only_ triggers for #GP accesses, so the
cases of valid kernel pointers that cross into a non-mapped page aren't
affected.

The intent of this is two-fold:

 - the uprobe/tracing accesses really do need to be more careful. In
   particular, from a portability standpoint it's just wrong to think
   that "a pointer is a pointer", and use the same logic for any random
   pointer value you find on the stack. It may _work_ on x86-64, but it
   doesn't necessarily work on other architectures (where the same
   pointer value can be either a kernel pointer _or_ a user pointer, and
   you really need to be much more careful in how you try to access it)

   The warning can hopefully end up being a reminder that just any
   random pointer access won't do.

 - Kees in particular wanted a way to actually report invalid uses of
   wild pointers to user space accessors, instead of just silently
   failing them. Automated fuzzers want a way to get reports if the
   kernel ever uses invalid values that the fuzzer fed it.

   The non-canonical address range is a fair chunk of the address space,
   and with this you can teach syzkaller to feed in invalid pointer
   values and find cases where we do not properly validate user
   addresses (possibly due to bad uses of "set_fs()").

Acked-by: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-04 10:08:28 -08:00
arch x86-64: add warning for non-canonical user access address dereferences 2019-03-04 10:08:28 -08:00
block for-linus-20190215 2019-02-15 09:12:28 -08:00
certs kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
crypto net: crypto set sk to NULL when af_alg_release. 2019-02-18 12:01:24 -08:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
drivers ARM: SoC fixes for v5.0 2019-03-02 16:43:15 -08:00
firmware kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
fs Merge branch 'akpm' (patches from Andrew) 2019-03-01 09:04:59 -08:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-02 08:46:34 -08:00
init revert "initramfs: cleanup incomplete rootfs" 2019-02-21 09:00:59 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel bpf: fix sanitation rewrite in case of non-pointers 2019-03-01 21:24:08 -08:00
lib kasan: turn off asan-stack for clang-8 and earlier 2019-03-01 09:02:33 -08:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm Merge branch 'akpm' (patches from Andrew) 2019-03-01 09:04:59 -08:00
net net: sit: fix memory leak in sit_init_net() 2019-03-02 00:53:23 -08:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-01-30 15:24:45 +01:00
scripts kasan: turn off asan-stack for clang-8 and earlier 2019-03-01 09:02:33 -08:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
sound sound fixes for 5.0 2019-02-20 09:42:52 -08:00
tools selftests: fixes for UDP GRO 2019-03-01 11:24:00 -08:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt kvm: properly check debugfs dentry before using it 2019-02-28 08:57:32 -08:00
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS CREDITS/MAINTAINERS: Retire parisc-linux.org email domain 2019-02-21 20:16:10 +01:00
Kbuild kbuild: use assignment instead of define ... endef for filechk_* rules 2019-01-06 10:22:35 +09:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
Makefile Linux 5.0 2019-03-03 15:21:29 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.