From: David Gow Date: Wed, 31 Jul 2024 07:30:29 +0000 (+0800) Subject: x86/uaccess: Zero the 8-byte get_range case on failure on 32-bit X-Git-Tag: v6.12~732^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=dd35a0933269c636635b6af89dc6fa1782791e56;p=platform%2Fkernel%2Flinux-amlogic.git 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 Signed-off-by: Thomas Gleixner Acked-by: Linus Torvalds Link: https://lore.kernel.org/all/20240731073031.4045579-1-davidgow@google.com --- 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