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| author | David Gow <davidgow@google.com> | 2024-07-31 09:30:29 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-08-01 21:19:10 +0200 |
| commit | dd35a0933269c636635b6af89dc6fa1782791e56 (patch) | |
| tree | 0ce39c696068b85f430febb2ae43c441aeff26af /arch/x86/lib/getuser.S | |
| parent | x86/mm: Fix pti_clone_entry_text() for i386 (diff) | |
| download | linux-dd35a0933269c636635b6af89dc6fa1782791e56.tar.xz linux-dd35a0933269c636635b6af89dc6fa1782791e56.zip | |
x86/uaccess: Zero the 8-byte get_range case on failure on 32-bit
While zeroing the upper 32 bits of an 8-byte getuser on 32-bit x86 was
fixed by commit 8c860ed825cb ("x86/uaccess: Fix missed zeroing of ia32 u64
get_user() range checking") it was broken again in commit 8a2462df1547
("x86/uaccess: Improve the 8-byte getuser() case").
This is because the register which holds the upper 32 bits (%ecx) is being
cleared _after_ the check_range, so if the range check fails, %ecx is never
cleared.
This can be reproduced with:
./tools/testing/kunit/kunit.py run --arch i386 usercopy
Instead, clear %ecx _before_ check_range in the 8-byte case. This
reintroduces a bit of the ugliness we were trying to avoid by adding
another #ifndef CONFIG_X86_64, but at least keeps check_range from needing
a separate bad_get_user_8 jump.
Fixes: 8a2462df1547 ("x86/uaccess: Improve the 8-byte getuser() case")
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/20240731073031.4045579-1-davidgow@google.com
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/lib/getuser.S | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S index a314622aa093..d066aecf8aeb 100644 --- a/arch/x86/lib/getuser.S +++ b/arch/x86/lib/getuser.S @@ -88,12 +88,14 @@ SYM_FUNC_END(__get_user_4) EXPORT_SYMBOL(__get_user_4) SYM_FUNC_START(__get_user_8) +#ifndef CONFIG_X86_64 + xor %ecx,%ecx +#endif check_range size=8 ASM_STAC #ifdef CONFIG_X86_64 UACCESS movq (%_ASM_AX),%rdx #else - xor %ecx,%ecx UACCESS movl (%_ASM_AX),%edx UACCESS movl 4(%_ASM_AX),%ecx #endif |