Commit 8c860ed8 authored by Kees Cook's avatar Kees Cook Committed by Dave Hansen
Browse files

x86/uaccess: Fix missed zeroing of ia32 u64 get_user() range checking 

When reworking the range checking for get_user(), the get_user_8() case
on 32-bit wasn't zeroing the high register. (The jump to bad_get_user_8
was accidentally dropped.) Restore the correct error handling
destination (and rename the jump to using the expected ".L" prefix).

While here, switch to using a named argument ("size") for the call
template ("%c4" to "%c[size]") as already used in the other call
templates in this file.

Found after moving the usercopy selftests to KUnit:

      # usercopy_test_invalid: EXPECTATION FAILED at
      lib/usercopy_kunit.c:278
      Expected val_u64 == 0, but
          val_u64 == -60129542144 (0xfffffff200000000)

Closes: https://lore.kernel.org/all/CABVgOSn=tb=Lj9SxHuT4_9MTjjKVxsq-ikdXC4kGHO4CfKVmGQ@mail.gmail.com


Fixes: b19b74bc ("x86/mm: Rework address range check in get_user() and put_user()")
Reported-by: default avatarDavid Gow <davidgow@google.com>
Signed-off-by: default avatarKees Cook <kees@kernel.org>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarQiuxu Zhuo <qiuxu.zhuo@intel.com>
Tested-by: default avatarDavid Gow <davidgow@google.com>
Link: https://lore.kernel.org/all/20240610210213.work.143-kees%40kernel.org
parent c625dabb

arch/x86/include/asm/uaccess.h

+2 −2
Original line number Diff line number Diff line
@@ -78,10 +78,10 @@ extern int __get_user_bad(void); 
	int __ret_gu;							\

	register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);		\

	__chk_user_ptr(ptr);						\

	asm volatile("call __" #fn "_%c4"				\

	asm volatile("call __" #fn "_%c[size]"				\

		     : "=a" (__ret_gu), "=r" (__val_gu),		\

			ASM_CALL_CONSTRAINT				\

		     : "0" (ptr), "i" (sizeof(*(ptr))));		\

		     : "0" (ptr), [size] "i" (sizeof(*(ptr))));		\

	instrument_get_user(__val_gu);					\

	(x) = (__force __typeof__(*(ptr))) __val_gu;			\

	__builtin_expect(__ret_gu, 0);					\

arch/x86/lib/getuser.S

+5 −1
Original line number Diff line number Diff line
@@ -44,7 +44,11 @@ 
	or %rdx, %rax

.else

	cmp $TASK_SIZE_MAX-\size+1, %eax

.if \size != 8

	jae .Lbad_get_user

.else

	jae .Lbad_get_user_8

.endif

	sbb %edx, %edx		/* array_index_mask_nospec() */

	and %edx, %eax

.endif
@@ -154,7 +158,7 @@ SYM_CODE_END(__get_user_handle_exception) 
#ifdef CONFIG_X86_32

SYM_CODE_START_LOCAL(__get_user_8_handle_exception)

	ASM_CLAC

bad_get_user_8:

.Lbad_get_user_8:

	xor %edx,%edx

	xor %ecx,%ecx

	mov $(-EFAULT),%_ASM_AX