From c485658bae87faccd7aed540fd2ca3ab37992310 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 4 Mar 2014 16:35:51 +0100 Subject: net: sctp: fix skb leakage in COOKIE ECHO path of chunk->auth_chunk 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: [] kmemleak_alloc+0x4e/0xb0 [] kmem_cache_alloc+0xc8/0x210 [] skb_clone+0x49/0xb0 [] sctp_endpoint_bh_rcv+0x1d9/0x230 [sctp] [] sctp_inq_push+0x4c/0x70 [sctp] [] sctp_rcv+0x82e/0x9a0 [sctp] [] ip_local_deliver_finish+0xa8/0x210 [] nf_reinject+0xbf/0x180 [] nfqnl_recv_verdict+0x1d2/0x2b0 [nfnetlink_queue] [] nfnetlink_rcv_msg+0x14b/0x250 [nfnetlink] [] netlink_rcv_skb+0xa9/0xc0 [] nfnetlink_rcv+0x23f/0x408 [nfnetlink] [] netlink_unicast+0x168/0x250 [] netlink_sendmsg+0x2e1/0x3f0 [] sock_sendmsg+0x8b/0xc0 [] ___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 Cc: Vlad Yasevich Cc: Neil Horman Acked-by: Vlad Yasevich Acked-by: Neil Horman Signed-off-by: David S. Miller --- net/sctp/sm_make_chunk.c | 4 ++-- net/sctp/sm_statefuns.c | 5 ----- 2 files changed, 2 insertions(+), 7 deletions(-) (limited to 'net/sctp') diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c index 632090b961c3..3a1767ef3201 100644 --- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -1421,8 +1421,8 @@ static void sctp_chunk_destroy(struct sctp_chunk *chunk) BUG_ON(!list_empty(&chunk->list)); list_del_init(&chunk->transmitted_list); - /* 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); SCTP_DBG_OBJCNT_DEC(chunk); kmem_cache_free(sctp_chunk_cachep, chunk); diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index ae65b6b5973a..01e002430c85 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -760,7 +760,6 @@ sctp_disposition_t sctp_sf_do_5_1D_ce(struct net *net, /* Make sure that we and the peer are AUTH capable */ if (!net->sctp.auth_enable || !new_asoc->peer.auth_capable) { - kfree_skb(chunk->auth_chunk); sctp_association_free(new_asoc); return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); } @@ -775,10 +774,6 @@ sctp_disposition_t sctp_sf_do_5_1D_ce(struct net *net, auth.transport = chunk->transport; ret = sctp_sf_authenticate(net, 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) { sctp_association_free(new_asoc); return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); -- cgit v1.2.3