[patch 14/16] sctp: correct bounds check in sctp_setsockopt_auth_key

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: 0011-sctp-correct-bounds-check-in-sctp_setsockopt_auth_k.patch --]
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2.6.25-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Vlad Yasevich <vladislav.yasevich@hp.com>

[ Upstream commit 328fc47ea0bcc27d9afa69c3ad6e52431cadd76c ]

The bonds check to prevent buffer overlflow was not exactly
right.  It still allowed overflow of up to 8 bytes which is
sizeof(struct sctp_authkey).

Since optlen is already checked against the size of that struct,
we are guaranteed not to cause interger overflow either.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/sctp/socket.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3072,7 +3072,7 @@ static int sctp_setsockopt_auth_key(stru
 		goto out;
 	}
 
-	if (authkey->sca_keylength > optlen) {
+	if (authkey->sca_keylength > optlen - sizeof(struct sctp_authkey)) {
 		ret = -EINVAL;
 		goto out;
 	}

--