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Subject[04/68] sctp: Fix out-of-bounds reading in sctp_asoc_get_hmac()
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------
From: Dan Rosenberg <drosenberg@vsecurity.com>

commit 51e97a12bef19b7e43199fc153cf9bd5f2140362 upstream.

The sctp_asoc_get_hmac() function iterates through a peer's hmac_ids
array and attempts to ensure that only a supported hmac entry is
returned. The current code fails to do this properly - if the last id
in the array is out of range (greater than SCTP_AUTH_HMAC_ID_MAX), the
id integer remains set after exiting the loop, and the address of an
out-of-bounds entry will be returned and subsequently used in the parent
function, causing potentially ugly memory corruption. This patch resets
the id integer to 0 on encountering an invalid id so that NULL will be
returned after finishing the loop if no valid ids are found.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Acked-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/auth.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -542,16 +542,20 @@ struct sctp_hmac *sctp_auth_asoc_get_hma
id = ntohs(hmacs->hmac_ids[i]);

/* Check the id is in the supported range */
- if (id > SCTP_AUTH_HMAC_ID_MAX)
+ if (id > SCTP_AUTH_HMAC_ID_MAX) {
+ id = 0;
continue;
+ }

/* See is we support the id. Supported IDs have name and
* length fields set, so that we can allocated and use
* them. We can safely just check for name, for without the
* name, we can't allocate the TFM.
*/
- if (!sctp_hmac_list[id].hmac_name)
+ if (!sctp_hmac_list[id].hmac_name) {
+ id = 0;
continue;
+ }

break;
}



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