From: Peter Zijlstra Date: Thu, 29 Aug 2019 08:24:45 +0000 (+0200) Subject: x86/uaccess: Don't leak the AC flags into __get_user() argument evaluation X-Git-Tag: v5.3-rc8~18^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=9b8bd476e78e89c9ea26c3b435ad0201c3d7dbf5;p=linux.git x86/uaccess: Don't leak the AC flags into __get_user() argument evaluation 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 Reported-by: Randy Dunlap Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Josh Poimboeuf Reviewed-by: Thomas Gleixner Cc: broonie@kernel.org Cc: sfr@canb.auug.org.au Cc: akpm@linux-foundation.org Cc: Randy Dunlap Cc: mhocko@suse.cz Cc: Josh Poimboeuf Link: https://lkml.kernel.org/r/20190829082445.GM2369@hirez.programming.kicks-ass.net --- diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 9c4435307ff8..35c225ede0e4 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -444,8 +444,10 @@ __pu_label: \ ({ \ 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); \