linux-kernel - [PATCH] binfmt_misc: Fix compilation error in parse

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Date:	Sat, 21 Jan 2012 20:02:37 +0100
From:	Szymon Janc <szymon@...c.net.pl>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Szymon Janc <szymon@...c.net.pl>
Subject: [PATCH] binfmt_misc: Fix compilation error in parse_command()

This fix compilation error with CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
enabled. It looks like gcc 4.6.2 is not able to prove that count
is within sizeof(s) bounds (although it is).

  CC [M]  fs/binfmt_misc.o
In file included from arch/x86/include/asm/uaccess.h:573:0,
                 from include/linux/uaccess.h:5,
                 from include/linux/highmem.h:7,
                 from include/linux/pagemap.h:10,
                 from fs/binfmt_misc.c:26:
In function ‘copy_from_user’,
    inlined from ‘parse_command.part.1’ at fs/binfmt_misc.c:421:20:
arch/x86/include/asm/uaccess_32.h:211:26: error: call to ‘copy_from_user_overflow’ declared with attribute error: copy_from_user() buffer size is not provably correct
make[1]: *** [fs/binfmt_misc.o] Error 1
make: *** [fs] Error 2

Signed-off-by: Szymon Janc <szymon@...c.net.pl>
---
 fs/binfmt_misc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a9198df..4879d35 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -418,7 +418,7 @@ static int parse_command(const char __user *buffer, size_t count)
 		return 0;
 	if (count > 3)
 		return -EINVAL;
-	if (copy_from_user(s, buffer, count))
+	if (copy_from_user(s, buffer, min(count, sizeof(s))))
 		return -EFAULT;
 	if (s[count-1] == '\n')
 		count--;
-- 
1.7.8.3


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