linux-kernel - [PATCH] compat: fix use of an uninitialized variable in compat_sys_io

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Date:	Fri, 24 Dec 2010 18:16:26 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jeff Moyer <jmoyer@...hat.com>
Subject: [PATCH] compat: fix use of an uninitialized variable in compat_sys_io_setup()

The upper bytes of ctx64 might contain garbages because it was
set by get_user() which copied only lower 4 bytes as its second
argument points to. Since sys_io_setup() requires its argumet
is properly initialized to 0 we should set it explicitly.

On x86, this was not a problem since its implementation of
get_user() does a C assignment so that it can fill upper bytes
with 0's. But other archs that use __get_user_asm() or something
might have a problem.

Signed-off-by: Namhyung Kim <namhyung@...il.com>
Cc: Jeff Moyer <jmoyer@...hat.com>
---
 fs/compat.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/compat.c b/fs/compat.c
index 4376e07febbb..b074e9f79148 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -526,7 +526,7 @@ asmlinkage long
 compat_sys_io_setup(unsigned nr_reqs, u32 __user *ctx32p)
 {
 	long ret;
-	aio_context_t ctx64;
+	aio_context_t ctx64 = 0;
 
 	mm_segment_t oldfs = get_fs();
 	if (unlikely(get_user(ctx64, ctx32p)))
-- 
1.7.3.4.600.g982838b0

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