kernel/linux.git/net/sctp, branch v5.10.268

sctp: avoid auth_enable sysctl UAF during netns teardown

2026-08-23T12:16:26+00:00

[ Upstream commit f8d5e7846025f4ab15a461235f8ebae9094a361a ] proc_sctp_do_auth() updates the SCTP control socket after changing net.sctp.auth_enable. The handler gets the per-net SCTP state from ctl->data, so an already opened sysctl file can still target a network namespace while that namespace is being torn down. SCTP previously registered its per-net sysctls from sctp_defaults_init(), while the control socket is created later from sctp_ctrlsock_init(). This exposed a window during initialization where auth_enable was writable before net->sctp.ctl_sock existed, and a teardown window where auth_enable stayed writable after inet_ctl_sock_destroy() had released the control socket. Move the per-net SCTP sysctl registration into sctp_ctrlsock_init() after sctp_ctl_sock_init() succeeds, and unregister the sysctl table before destroying the control socket in sctp_ctrlsock_exit(). If sysctl registration fails after the control socket was created, destroy the control socket in the same init path. Make sctp_sysctl_net_unregister() tolerate a missing header and clear the saved pointer so init-error and exit paths can safely share the unregister helper. Fixes: 15649fd5415e ("sctp: sysctl: auth_enable: avoid using current->nsproxy") Cc: stable@vger.kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Co-developed-by: Qi Tang Signed-off-by: Qi Tang Signed-off-by: Zhiling Zou Signed-off-by: Ren Wei Acked-by: Xin Long Link: https://patch.msgid.link/390cd5e91ed60eea27b0b64d0468301a9e73b808.1784033357.git.roxy520tt@gmail.com Signed-off-by: Jakub Kicinski [ dropped the missing `l3mdev_accept` context block and kept 6.1's non-const `struct ctl_table *table` declaration ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sctp: clear new_transport when removing a peer

2026-08-19T15:12:15+00:00

commit beb33f8ee1ca83acddb2a5ae80f3d22ec550b4c3 upstream. sctp_process_asconf_param() stores a newly added peer transport in asoc->new_transport. After all parameters in the ASCONF chunk have been processed, sctp_sf_do_asconf() uses this pointer to send a HEARTBEAT to the new transport. An authenticated ASCONF from a remote SCTP peer can add a transport and remove it again with a wildcard DEL-IP parameter in the same chunk. The wildcard deletion preserves the transport on which the ASCONF arrived, but removes the newly added transport through sctp_assoc_del_nonprimary_peers(). The removal does not clear asoc->new_transport, leaving it pointing to the removed transport. sctp_sf_do_asconf() then creates a HEARTBEAT whose chunk->transport points to the removed transport without holding a transport reference. During local address replacement, src_out_of_asoc_ok keeps this HEARTBEAT on control_chunk_list. After the transport is freed by RCU, a successful ASCONF_ACK for the replacement address releases the queued HEARTBEAT and sctp_outq_select_transport() reads the freed transport's state. The issue was found during a static audit of SCTP objects. With an authenticated peer, the reproducer triggered the same KASAN report in 2 of 2 unpatched runs on a KASAN-enabled netdev/main kernel: BUG: KASAN: slab-use-after-free in sctp_outq_select_transport Read of size 4 at addr ffff88800b9bd95c by task python3/197 Call Trace: sctp_outq_select_transport+0x549/0x8b0 [sctp] sctp_outq_flush+0x306/0x2c60 [sctp] sctp_transport_immediate_rtx+0xaf/0x260 [sctp] sctp_process_asconf_ack+0xa48/0xf70 [sctp] Allocated by task 197: sctp_transport_new+0x68/0x650 [sctp] sctp_assoc_add_peer+0x258/0x12a0 [sctp] sctp_process_asconf+0x5e9/0x1090 [sctp] Last potentially related work creation: __call_rcu_common.constprop.0+0x77/0xb70 sctp_assoc_del_nonprimary_peers+0x7c/0xd0 [sctp] sctp_process_asconf+0xd9c/0x1090 [sctp] The first invalid access was a four-byte read of transport->state at net/sctp/outqueue.c:833. The same reproducer completed the full authenticated ASCONF and local-address replacement sequence with this change without a KASAN report or oops. Clear new_transport when its peer is removed, before it can be used to create the HEARTBEAT. Fixes: 6af29ccc223b ("sctp: Bundle HEAERTBEAT into ASCONF_ACK") Cc: stable@vger.kernel.org Signed-off-by: Qing Ming Acked-by: Xin Long Link: https://patch.msgid.link/20260811152803.5629-1-a0yami@mailbox.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

sctp: fix use-after-free of cached ASCONF chunk

2026-08-19T15:12:15+00:00

commit 8c283e7b56adce00193837f3311b06662466fb21 upstream. addip_last_asconf caches the outstanding outbound ASCONF chunk. The normal ASCONF-ACK completion path releases the chunk and clears the pointer. However, sctp_asconf_queue_teardown() releases the cached chunk without clearing addip_last_asconf. During peer restart handling, sctp_sf_do_dupcook_a() queues SCTP_CMD_PURGE_ASCONF_QUEUE, which invokes sctp_asconf_queue_teardown() while the association remains alive and leaves the pointer dangling. A delayed authenticated ASCONF-ACK can then reach sctp_sf_do_asconf_ack(), which accesses the stale chunk and passes it to sctp_process_asconf_ack(), causing a use-after-free and a second release. Clearing the pointer exposes a race with T4 expiry. Peer restart handling queues the timer stop before the purge, but SCTP_CMD_TIMER_STOP uses timer_delete(), which does not wait for a callback already running on another CPU. Such a callback can reach sctp_sf_t4_timer_expire() after the purge and dereference NULL. Clear addip_last_asconf after releasing the cached chunk, and make sctp_sf_t4_timer_expire() consume a stale T4 expiry if no outstanding ASCONF remains. Fixes: a000c01e60e4 ("sctp: stop pending timers and purge queues when peer restart asoc") Cc: stable@vger.kernel.org Suggested-by: Xin Long Signed-off-by: Yuxiang Yang Acked-by: Xin Long Link: https://patch.msgid.link/20260809043806.2768302-1-yangyx22@mails.tsinghua.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

sctp: keep chunk->transport in step with the list it is queued on

2026-08-19T15:12:15+00:00

commit 9f2cf069a9a72a2d6b97ca8b4c70e714aac99749 upstream. __sctp_outq_flush_rtx() moves a gap-acked chunk onto another transport's transmitted list without updating chunk->transport: if (chunk->tsn_gap_acked) { list_move_tail(&chunk->transmitted_list, &transport->transmitted); continue; } The chunk then sits on a live transport's list while chunk->transport still names a different one. If that transport is removed - sctp_assoc_rm_peer() from an ASCONF Delete-IP - sctp_transport_free() RCU-frees it and the chunk is left with a dangling pointer. sctp_assoc_rm_peer() scrubs peer->transmitted and asoc->outqueue.out_chunk_list, but the chunk is on neither. The pointer is not followed while tsn_gap_acked is set. A SACK that reneges on the TSN clears the flag, and the next SACK reaches tchunk->transport->flight_size -= sctp_data_size(tchunk); inside the freed transport. KASAN reports a slab-use-after-free read in sctp_check_transmitted(), freed from sctp_assoc_rm_peer(). Both the removal and the SACKs come from the association peer. Set chunk->transport at the move. The ordinary resend path needs nothing: it reaches its list_move_tail() only after sctp_packet_append_chunk() returned SCTP_XMIT_OK, and __sctp_packet_append_chunk() has rebound the chunk by then. Discovered by XBOW, triaged by Baul Lee Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Acked-by: Xin Long Link: https://patch.msgid.link/20260729160028.54546-1-baul.lee@xbow.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

sctp: extract sctp_v4_err_handle function from sctp_v4_err

2026-08-19T15:12:12+00:00

[ Upstream commit d83060759a652ccb64d7486fe38c8347b4a64048 ] This patch is to extract sctp_v4_err_handle() from sctp_v4_err() to only handle the icmp err after the sock lookup, and it also makes the code clearer. sctp_v4_err_handle() will be used in sctp over udp's err handling in the following patch. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller Stable-dep-of: af0e5cdd031f ("tls: don't abort the connection on signal-interrupted sends") Signed-off-by: Sasha Levin

sctp: extract sctp_v6_err_handle function from sctp_v6_err

2026-08-19T15:12:12+00:00

[ Upstream commit f6549bd37b927655c6fecad88428a731cd8a4a34 ] This patch is to extract sctp_v6_err_handle() from sctp_v6_err() to only handle the icmp err after the sock lookup, and it also makes the code clearer. sctp_v6_err_handle() will be used in sctp over udp's err handling in the following patch. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller Stable-dep-of: af0e5cdd031f ("tls: don't abort the connection on signal-interrupted sends") Signed-off-by: Sasha Levin

sctp: remove the unessessary hold for idev in sctp_v6_err

2026-08-19T15:12:12+00:00

[ Upstream commit 237a6a2e318c1ed7429e72f2640054bdda91646f ] Same as in tcp_v6_err() and __udp6_lib_err(), there's no need to hold idev in sctp_v6_err(), so just call __in6_dev_get() instead. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller Stable-dep-of: af0e5cdd031f ("tls: don't abort the connection on signal-interrupted sends") Signed-off-by: Sasha Levin

sctp: clear control chunk transport if it is being removed

2026-08-19T15:12:12+00:00

[ Upstream commit c9158ceaf27780ef64534ad72f44ffde3f8ccc49 ] sctp_make_heartbeat_ack() caches the destination transport in chunk->transport without taking a reference. When src_out_of_asoc_ok is enabled, the HEARTBEAT ACK may remain queued on control_chunk_list instead of being transmitted immediately. If the peer transport is removed while the chunk is still queued, sctp_assoc_rm_peer() drops the transport and schedules it for RCU freeing, but only clears cached transport pointers in out_chunk_list. The queued control chunk therefore retains a dangling transport pointer. Once an ASCONF_ACK clears the suppression and the queued control chunk is transmitted, SCTP dereferences the stale transport pointer, leading to a use-after-free. Fix this by also clearing chunk->transport for queued control chunks in control_chunk_list when removing the transport. Fixes: 8a07eb0a50ae ("sctp: Add ASCONF operation on the single-homed host") Reported-by: Daniele Linguaglossa Signed-off-by: Xin Long Link: https://patch.msgid.link/7e1168cb722132152a29d47e5eafaeac4a3bf6f3.1785943120.git.lucien.xin@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

sctp: fix addip_serial increment on ASCONF_ACK allocation failure

2026-08-19T15:12:12+00:00

[ Upstream commit aa2e13ae8d3cbe2c15ef4f7e971b2de0832794aa ] In sctp_process_asconf(), when sctp_make_asconf_ack() fails to allocate the ASCONF_ACK chunk due to memory pressure, the code jumps to the done label where asoc->peer.addip_serial is unconditionally incremented. This leaves the peer's ASCONF (serial N) unacknowledged while the local endpoint now expects serial N+1. When the peer retransmits serial N, it falls into the serial < addip_serial + 1 branch , which attempts to look up a cached ACK for serial N. No cached ACK exists since the allocation failed, so the retransmission is silently discarded. The peer eventually times out and ABORTs the association. Move the addip_serial increment inside the if (asconf_ack) block so that the serial number is only advanced when the ASCONF_ACK is successfully created and cached. This way, on allocation failure, the serial number is unchanged and the peer's retransmitted ASCONF will be correctly re-processed. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Qing Luo Acked-by: Xin Long Link: https://patch.msgid.link/20260804025514.241767-1-l1138897701@163.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

sctp: prevent peer transport count overflow

2026-08-19T15:12:09+00:00

commit bd0e9289e2642f6a5c54faad304ce0f41e926d22 upstream. sctp_assoc_add_peer() increments the association's 16-bit transport_count for every new unique peer. Adding the 65,536th transport wraps the count to zero. SCTP sock_diag uses transport_count to reserve the INET_DIAG_PEERS payload, then copies one sockaddr_storage for every entry in transport_addr_list. After the wrap, a diagnostic dump reserves an empty payload and writes 8 MiB of peer addresses past the skb tail. Reject a new unique peer when transport_count has reached U16_MAX. Perform the check after the existing-peer lookup so a duplicate address continues to return its existing transport at the limit. Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file") Cc: stable@vger.kernel.org Signed-off-by: Asim Viladi Oglu Manizada Acked-by: Xin Long Link: https://patch.msgid.link/20260725032053.521705-1-manizada@pm.me Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman