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17 May 2024, 11:00:25 UTC
Revision 2a418cf3f5f1caf911af288e978d61c9844b0695 authored by Andy Lutomirski on 23 February 2019, 01:17:04 UTC, committed by Borislav Petkov on 25 February 2019, 19:17:05 UTC 
x86/uaccess: Don't leak the AC flag into __put_user() value evaluation
 
When calling __put_user(foo(), ptr), the __put_user() macro would call
foo() in between __uaccess_begin() and __uaccess_end().  If that code
were buggy, then those bugs would be run without SMAP protection.

Fortunately, there seem to be few instances of the problem in the
kernel. Nevertheless, __put_user() should be fixed to avoid doing this.
Therefore, evaluate __put_user()'s argument before setting AC.

This issue was noticed when an objtool hack by Peter Zijlstra complained
about genregs_get() and I compared the assembly output to the C source.

 [ bp: Massage commit message and fixed up whitespace. ]

Fixes: 11f1a4b9755f ("x86: reorganize SMAP handling in user space accesses")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190225125231.845656645@infradead.org
1 parent f331e76
Raw File
Tip revision: 2a418cf3f5f1caf911af288e978d61c9844b0695 authored by Andy Lutomirski on 23 February 2019, 01:17:04 UTC
x86/uaccess: Don't leak the AC flag into __put_user() value evaluation
Tip revision: 2a418cf
Kconfig 
# SPDX-License-Identifier: GPL-2.0
#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
#
mainmenu "Linux/$(ARCH) $(KERNELVERSION) Kernel Configuration"

comment "Compiler: $(CC_VERSION_TEXT)"

source "scripts/Kconfig.include"

source "init/Kconfig"

source "kernel/Kconfig.freezer"

source "fs/Kconfig.binfmt"

source "mm/Kconfig"

source "net/Kconfig"

source "drivers/Kconfig"

source "fs/Kconfig"

source "security/Kconfig"

source "crypto/Kconfig"

source "lib/Kconfig"

source "lib/Kconfig.debug"
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