diff options
authorDaniel Borkmann <dborkman@redhat.com>2014-03-04 16:35:51 +0100
committerWilly Tarreau <w@1wt.eu>2014-05-19 07:54:15 +0200
commit3c3e5e546a2a8fe6b2d5d5e5e3385430999ce585 (patch)
parent57b7a1c227f4d069878e9d4199a11e53e99c3240 (diff)
net: sctp: fix skb leakage in COOKIE ECHO path of chunk->auth_chunk
[ Upstream commit c485658bae87faccd7aed540fd2ca3ab37992310 ] While working on ec0223ec48a9 ("net: sctp: fix sctp_sf_do_5_1D_ce to verify if we/peer is AUTH capable"), we noticed that there's a skb memory leakage in the error path. Running the same reproducer as in ec0223ec48a9 and by unconditionally jumping to the error label (to simulate an error condition) in sctp_sf_do_5_1D_ce() receive path lets kmemleak detector bark about the unfreed chunk->auth_chunk skb clone: Unreferenced object 0xffff8800b8f3a000 (size 256): comm "softirq", pid 0, jiffies 4294769856 (age 110.757s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 89 ab 75 5e d4 01 58 13 00 00 00 00 00 00 00 00 ..u^..X......... backtrace: [<ffffffff816660be>] kmemleak_alloc+0x4e/0xb0 [<ffffffff8119f328>] kmem_cache_alloc+0xc8/0x210 [<ffffffff81566929>] skb_clone+0x49/0xb0 [<ffffffffa0467459>] sctp_endpoint_bh_rcv+0x1d9/0x230 [sctp] [<ffffffffa046fdbc>] sctp_inq_push+0x4c/0x70 [sctp] [<ffffffffa047e8de>] sctp_rcv+0x82e/0x9a0 [sctp] [<ffffffff815abd38>] ip_local_deliver_finish+0xa8/0x210 [<ffffffff815a64af>] nf_reinject+0xbf/0x180 [<ffffffffa04b4762>] nfqnl_recv_verdict+0x1d2/0x2b0 [nfnetlink_queue] [<ffffffffa04aa40b>] nfnetlink_rcv_msg+0x14b/0x250 [nfnetlink] [<ffffffff815a3269>] netlink_rcv_skb+0xa9/0xc0 [<ffffffffa04aa7cf>] nfnetlink_rcv+0x23f/0x408 [nfnetlink] [<ffffffff815a2bd8>] netlink_unicast+0x168/0x250 [<ffffffff815a2fa1>] netlink_sendmsg+0x2e1/0x3f0 [<ffffffff8155cc6b>] sock_sendmsg+0x8b/0xc0 [<ffffffff8155d449>] ___sys_sendmsg+0x369/0x380 What happens is that commit bbd0d59809f9 clones the skb containing the AUTH chunk in sctp_endpoint_bh_rcv() when having the edge case that an endpoint requires COOKIE-ECHO chunks to be authenticated: ---------- INIT[RANDOM; CHUNKS; HMAC-ALGO] ----------> <------- INIT-ACK[RANDOM; CHUNKS; HMAC-ALGO] --------- ------------------ AUTH; COOKIE-ECHO ----------------> <-------------------- COOKIE-ACK --------------------- When we enter sctp_sf_do_5_1D_ce() and before we actually get to the point where we process (and subsequently free) a non-NULL chunk->auth_chunk, we could hit the "goto nomem_init" path from an error condition and thus leave the cloned skb around w/o freeing it. The fix is to centrally free such clones in sctp_chunk_destroy() handler that is invoked from sctp_chunk_free() after all refs have dropped; and also move both kfree_skb(chunk->auth_chunk) there, so that chunk->auth_chunk is either NULL (since sctp_chunkify() allocs new chunks through kmem_cache_zalloc()) or non-NULL with a valid skb pointer. chunk->skb and chunk->auth_chunk are the only skbs in the sctp_chunk structure that need to be handeled. While at it, we should use consume_skb() for both. It is the same as dev_kfree_skb() but more appropriately named as we are not a device but a protocol. Also, this effectively replaces the kfree_skb() from both invocations into consume_skb(). Functions are the same only that kfree_skb() assumes that the frame was being dropped after a failure (e.g. for tools like drop monitor), usage of consume_skb() seems more appropriate in function sctp_chunk_destroy() though. Fixes: bbd0d59809f9 ("[SCTP]: Implement the receive and verification of AUTH chunk") Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Vlad Yasevich <yasevich@gmail.com> Cc: Neil Horman <nhorman@tuxdriver.com> Acked-by: Vlad Yasevich <vyasevich@gmail.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Willy Tarreau <w@1wt.eu>
2 files changed, 2 insertions, 6 deletions
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index feedee7afa2c..22d4ed85248b 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1356,8 +1356,8 @@ static void sctp_chunk_destroy(struct sctp_chunk *chunk)
- /* Free the chunk skb data and the SCTP_chunk stub itself. */
- dev_kfree_skb(chunk->skb);
+ consume_skb(chunk->skb);
+ consume_skb(chunk->auth_chunk);
kmem_cache_free(sctp_chunk_cachep, chunk);
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index d43002b7a181..6da01717ca9f 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -762,10 +762,6 @@ sctp_disposition_t sctp_sf_do_5_1D_ce(const struct sctp_endpoint *ep,
auth.transport = chunk->transport;
ret = sctp_sf_authenticate(ep, new_asoc, type, &auth);
- /* We can now safely free the auth_chunk clone */
- kfree_skb(chunk->auth_chunk);
if (ret != SCTP_IERROR_NO_ERROR) {
return sctp_sf_pdiscard(ep, asoc, type, arg, commands);