This is a note to let you know that I've just added the patch titled sctp: fix the processing for INIT_ACK chunk to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sctp-fix-the-processing-for-init_ack-chunk.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 88c24a5a6379f605a15d231a5bd0245b0f3e951a Author: Xin Long <lucien.xin@xxxxxxxxx> Date: Wed Oct 20 07:42:43 2021 -0400 sctp: fix the processing for INIT_ACK chunk [ Upstream commit 438b95a7c98f77d51cbf4db021f41b602d750a3f ] Currently INIT_ACK chunk in non-cookie_echoed state is processed in sctp_sf_discard_chunk() to send an abort with the existent asoc's vtag if the chunk length is not valid. But the vtag in the chunk's sctphdr is not verified, which may be exploited by one to cook a malicious chunk to terminal a SCTP asoc. sctp_sf_discard_chunk() also is called in many other places to send an abort, and most of those have this problem. This patch is to fix it by sending abort with the existent asoc's vtag only if the vtag from the chunk's sctphdr is verified in sctp_sf_discard_chunk(). Note on sctp_sf_do_9_1_abort() and sctp_sf_shutdown_pending_abort(), the chunk length has been verified before sctp_sf_discard_chunk(), so replace it with sctp_sf_discard(). On sctp_sf_do_asconf_ack() and sctp_sf_do_asconf(), move the sctp_chunk_length_valid check ahead of sctp_sf_discard_chunk(), then replace it with sctp_sf_discard(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index 9bfa8cca9974..672e5308839b 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -2343,7 +2343,7 @@ enum sctp_disposition sctp_sf_shutdown_pending_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -2389,7 +2389,7 @@ enum sctp_disposition sctp_sf_shutdown_sent_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -2659,7 +2659,7 @@ enum sctp_disposition sctp_sf_do_9_1_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -3865,6 +3865,11 @@ enum sctp_disposition sctp_sf_do_asconf(struct net *net, return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); } + /* Make sure that the ASCONF ADDIP chunk has a valid length. */ + if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_addip_chunk))) + return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, + commands); + /* ADD-IP: Section 4.1.1 * This chunk MUST be sent in an authenticated way by using * the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk @@ -3873,13 +3878,7 @@ enum sctp_disposition sctp_sf_do_asconf(struct net *net, */ if (!asoc->peer.asconf_capable || (!net->sctp.addip_noauth && !chunk->auth)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, - commands); - - /* Make sure that the ASCONF ADDIP chunk has a valid length. */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_addip_chunk))) - return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, - commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); hdr = (struct sctp_addiphdr *)chunk->skb->data; serial = ntohl(hdr->serial); @@ -4008,6 +4007,12 @@ enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net, return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); } + /* Make sure that the ADDIP chunk has a valid length. */ + if (!sctp_chunk_length_valid(asconf_ack, + sizeof(struct sctp_addip_chunk))) + return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, + commands); + /* ADD-IP, Section 4.1.2: * This chunk MUST be sent in an authenticated way by using * the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk @@ -4016,14 +4021,7 @@ enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net, */ if (!asoc->peer.asconf_capable || (!net->sctp.addip_noauth && !asconf_ack->auth)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, - commands); - - /* Make sure that the ADDIP chunk has a valid length. */ - if (!sctp_chunk_length_valid(asconf_ack, - sizeof(struct sctp_addip_chunk))) - return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, - commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); addip_hdr = (struct sctp_addiphdr *)asconf_ack->skb->data; rcvd_serial = ntohl(addip_hdr->serial); @@ -4595,6 +4593,9 @@ enum sctp_disposition sctp_sf_discard_chunk(struct net *net, { struct sctp_chunk *chunk = arg; + if (asoc && !sctp_vtag_verify(chunk, asoc)) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + /* Make sure that the chunk has a valid length. * Since we don't know the chunk type, we use a general * chunkhdr structure to make a comparison.