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Tiezhu Yang 67d0662ce9 MIPS: Prevent READ_IMPLIES_EXEC propagation 
In the MIPS architecture, we should clear the security-relevant
flag READ_IMPLIES_EXEC in the function SET_PERSONALITY2() of the
file arch/mips/include/asm/elf.h.

Otherwise, with this flag set, PROT_READ implies PROT_EXEC for
mmap to make memory executable that is not safe, because this
condition allows an attacker to simply jump to and execute bytes
that are considered to be just data [1].

In mm/mmap.c:
unsigned long do_mmap(struct file *file, unsigned long addr,
			unsigned long len, unsigned long prot,
			unsigned long flags, vm_flags_t vm_flags,
			unsigned long pgoff, unsigned long *populate,
			struct list_head *uf)
{
	[...]
	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
		if (!(file && path_noexec(&file->f_path)))
			prot |= PROT_EXEC;
	[...]
}

By the way, x86 and ARM64 have done the similar thing.

After commit 250c22777f ("x86_64: move kernel"), in the file
arch/x86/kernel/process_64.c:
void set_personality_64bit(void)
{
	[...]
	current->personality &= ~READ_IMPLIES_EXEC;
}

After commit 48f99c8ec0 ("arm64: Preventing READ_IMPLIES_EXEC
propagation"), in the file arch/arm64/include/asm/elf.h:
#define SET_PERSONALITY(ex)						\
({									\
	clear_thread_flag(TIF_32BIT);					\
	current->personality &= ~READ_IMPLIES_EXEC;			\
})

[1] https://insights.sei.cmu.edu/cert/2014/02/feeling-insecure-blame-your-parent.html

Reported-by: Juxin Gao <gaojuxin@loongson.cn>
Co-developed-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
2020-07-16 13:18:19 +02:00
arch MIPS: Prevent READ_IMPLIES_EXEC propagation 2020-07-16 13:18:19 +02:00
block Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
certs
crypto Merge branch 'rwonce/rework' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux 2020-06-10 14:46:54 -07:00
Documentation dt-bindings: MIPS: Add X1830 based CU1830-Neo and fix bug in CU1000-Neo. 2020-07-16 10:54:52 +02:00
drivers MIPS: Loongson: Fix boot warning about hwmon_device_register() 2020-07-16 10:49:55 +02:00
fs for-5.8-part2-tag 2020-06-14 09:47:25 -07:00
include Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
init Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
lib Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
LICENSES
mm Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
samples binderfs: add gitignore for generated sample program 2020-06-13 13:41:24 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
security Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
sound Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
usr
virt MIPS: 2020-06-12 11:05:52 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore modpost: generate vmlinux.symvers and reuse it for the second modpost 2020-06-06 23:38:12 +09:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'i2c/for-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2020-06-13 13:12:38 -07:00
Makefile Linux 5.8-rc1 2020-06-14 12:45:04 -07:00
README

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.