[PATCH] sctp: integer overflow in sctp_auth_create_key()

The previous commit 30c2235c is incomplete and cannot prevent integer
overflows. For example, when key_len is 0x80000000 (INT_MAX + 1), the
left-hand side of the check, (INT_MAX - key_len), which is unsigned,
becomes 0xffffffff (UINT_MAX) and bypasses the check.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
---
net/sctp/auth.c |    2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 865e68f..989e0fd 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c

@@ -82,7 +82,7 @@ static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp)

	struct sctp_auth_bytes *key;

	/* Verify that we are not going to overflow INT_MAX */
-	if ((INT_MAX - key_len) < sizeof(struct sctp_auth_bytes))
+	if (key_len > INT_MAX - sizeof(struct sctp_auth_bytes))
		return NULL;

	/* Allocate the shared key */
-- 
1.7.5.4

From: Xi Wang <xi.wang@gmail.com>
Date: Tue, 22 Nov 2011 20:55:30 -0500

The previous commit 30c2235c is incomplete and cannot prevent integer
overflows. For example, when key_len is 0x80000000 (INT_MAX + 1), the
left-hand side of the check, (INT_MAX - key_len), which is unsigned,
becomes 0xffffffff (UINT_MAX) and bypasses the check.

Signed-off-by: Xi Wang <xi.wang@gmail.com>

Applied, but I had to apply your patch by hand because it was
corrupted by your email client.

Please fix this problem because I am not applying any other patch
you've submitted which has this issue.

Sorry my bad.

BTW it seems that the patch was not applied correctly either in
the commit a5e5c374 --- it says "No differences found".

Can you please apply the new patch v2?  Thanks.

- xi

On Nov 29, 2011, at 1:19 AM, David Miller wrote:

Applied, but I had to apply your patch by hand because it was
corrupted by your email client.

Please fix this problem because I am not applying any other patch
you've submitted which has this issue.

From: Xi Wang <xi.wang@gmail.com>
Date: Tue, 29 Nov 2011 14:31:30 -0500

a5e5c374 --- it says "No differences found".

Can you please apply the new patch v2?  Thanks.

Sigh, probably a side effect of how your patch was corrupted
and how I tried to fix it up by hand :-/

Ok, I'll apply v2, thanks.