[patch V5 03/12] x86/uaccess: Use unsafe wrappers for ASM GOTO
From: Thomas Gleixner <hidden>
Date: 2025-10-27 08:43:49
Also in:
linux-arm-kernel, linux-fsdevel, linux-riscv, linux-s390, lkml
ASM GOTO is miscompiled by GCC when it is used inside a auto cleanup scope:
bool foo(u32 __user *p, u32 val)
{
scoped_guard(pagefault)
unsafe_put_user(val, p, efault);
return true;
efault:
return false;
}
It ends up leaking the pagefault disable counter in the fault path. clang
at least fails the build.
Rename unsafe_*_user() to arch_unsafe_*_user() which makes the generic
uaccess header wrap it with a local label that makes both compilers emit
correct code. Same for the kernel_nofault() variants.
Signed-off-by: Thomas Gleixner <redacted>
Cc: x86@kernel.org
---
arch/x86/include/asm/uaccess.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h@@ -528,18 +528,18 @@ static __must_check __always_inline bool #define user_access_save() smap_save() #define user_access_restore(x) smap_restore(x) -#define unsafe_put_user(x, ptr, label) \ +#define arch_unsafe_put_user(x, ptr, label) \ __put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label) #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT -#define unsafe_get_user(x, ptr, err_label) \ +#define arch_unsafe_get_user(x, ptr, err_label) \ do { \ __inttype(*(ptr)) __gu_val; \ __get_user_size(__gu_val, (ptr), sizeof(*(ptr)), err_label); \ (x) = (__force __typeof__(*(ptr)))__gu_val; \ } while (0) #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT -#define unsafe_get_user(x, ptr, err_label) \ +#define arch_unsafe_get_user(x, ptr, err_label) \ do { \ int __gu_err; \ __inttype(*(ptr)) __gu_val; \
@@ -618,11 +618,11 @@ do { \ } while (0) #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT -#define __get_kernel_nofault(dst, src, type, err_label) \ +#define arch_get_kernel_nofault(dst, src, type, err_label) \ __get_user_size(*((type *)(dst)), (__force type __user *)(src), \ sizeof(type), err_label) #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT -#define __get_kernel_nofault(dst, src, type, err_label) \ +#define arch_get_kernel_nofault(dst, src, type, err_label) \ do { \ int __kr_err; \ \
@@ -633,7 +633,7 @@ do { \ } while (0) #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT -#define __put_kernel_nofault(dst, src, type, err_label) \ +#define arch_put_kernel_nofault(dst, src, type, err_label) \ __put_user_size(*((type *)(src)), (__force type __user *)(dst), \ sizeof(type), err_label)