From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 9b8bd476e78e89c9ea26c3b435ad0201c3d7dbf5 ]
Identical to __put_user(); the __get_user() argument evalution will too leak UBSAN crud into the __uaccess_begin() / __uaccess_end() region. While uncommon this was observed to happen for:
drivers/xen/gntdev.c: if (__get_user(old_status, batch->status[i]))
where UBSAN added array bound checking.
This complements commit:
6ae865615fc4 ("x86/uaccess: Dont leak the AC flag into __put_user() argument evaluation")
Tested-by Sedat Dilek sedat.dilek@gmail.com Reported-by: Randy Dunlap rdunlap@infradead.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Josh Poimboeuf jpoimboe@redhat.com Reviewed-by: Thomas Gleixner tglx@linutronix.de Cc: broonie@kernel.org Cc: sfr@canb.auug.org.au Cc: akpm@linux-foundation.org Cc: Randy Dunlap rdunlap@infradead.org Cc: mhocko@suse.cz Cc: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/20190829082445.GM2369@hirez.programming.kicks-ass.... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/uaccess.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 2177c7551ff77..9db8d8758ed3b 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -438,8 +438,10 @@ do { \ ({ \ int __gu_err; \ __inttype(*(ptr)) __gu_val; \ + __typeof__(ptr) __gu_ptr = (ptr); \ + __typeof__(size) __gu_size = (size); \ __uaccess_begin_nospec(); \ - __get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \ + __get_user_size(__gu_val, __gu_ptr, __gu_size, __gu_err, -EFAULT); \ __uaccess_end(); \ (x) = (__force __typeof__(*(ptr)))__gu_val; \ __builtin_expect(__gu_err, 0); \