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Message-Id: <20190919214811.103313365@linuxfoundation.org>
Date: Fri, 20 Sep 2019 00:04:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>, broonie@...nel.org,
sfr@...b.auug.org.au, akpm@...ux-foundation.org, mhocko@...e.cz,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 69/74] x86/uaccess: Dont leak the AC flags into __get_user() argument evaluation
From: Peter Zijlstra <peterz@...radead.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@...il.com>
Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: broonie@...nel.org
Cc: sfr@...b.auug.org.au
Cc: akpm@...ux-foundation.org
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: mhocko@...e.cz
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lkml.kernel.org/r/20190829082445.GM2369@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@...nel.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); \
--
2.20.1
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