kernel/linux.git/net/sctp/socket.c, branch v5.15.209

sctp: fix OOB write to userspace in sctp_getsockopt_peer_auth_chunks

2026-06-01T15:35:38+00:00

[ Upstream commit 0cf004ffb61cd32d140531c3a84afe975f9fc7ea ] sctp_getsockopt_peer_auth_chunks() checks that the caller's optval buffer is large enough for the peer AUTH chunk list with if (len < num_chunks) return -EINVAL; but then writes num_chunks bytes to p->gauth_chunks, which lives at offset offsetof(struct sctp_authchunks, gauth_chunks) == 8 inside optval. The check is missing the sizeof(struct sctp_authchunks) = 8-byte header. When the caller supplies len == num_chunks (for any num_chunks > 0) the test passes but copy_to_user() writes sizeof(struct sctp_authchunks) = 8 bytes past the declared buffer. The sibling function sctp_getsockopt_local_auth_chunks() at the next line already has the correct check: if (len < sizeof(struct sctp_authchunks) + num_chunks) return -EINVAL; Align the peer variant with its sibling. Reproducer confirms on v7.0-13-generic: an unprivileged userspace caller that opens a loopback SCTP association with AUTH enabled, queries num_chunks with a short optval, then issues the real getsockopt with len == num_chunks and sentinel bytes painted past the buffer observes those sentinel bytes overwritten with the peer's AUTH chunk type. The bytes written are under the peer's control but land in the caller's own userspace; this is not a kernel memory corruption, but it is a kernel-side contract violation that can silently corrupt adjacent userspace data. Fixes: 65b07e5d0d09 ("[SCTP]: API updates to suport SCTP-AUTH extensions.") Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Michael Bommarito Acked-by: Xin Long Link: https://patch.msgid.link/20260416031903.1447072-1-michael.bommarito@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL

2026-06-01T15:35:26+00:00

commit abb5f36771cc4c05899b34000829a787572a8817 upstream. The SCTP_SENDALL path in sctp_sendmsg() iterates ep->asocs with list_for_each_entry_safe(), which caches the next entry in @tmp before the loop body runs. The body calls sctp_sendmsg_to_asoc(), which may drop the socket lock inside sctp_wait_for_sndbuf(). While the lock is dropped, another thread can SCTP_SOCKOPT_PEELOFF the association cached in @tmp, migrating it to a new endpoint via sctp_sock_migrate() (list_del_init() + list_add_tail() to newep->asocs), and optionally close the new socket which frees the association via kfree_rcu(). The cached @tmp can also be freed by a network ABORT for that association, processed in softirq while the lock is dropped. sctp_wait_for_sndbuf() revalidates @asoc (the current entry) on re-lock via the "sk != asoc->base.sk" and "asoc->base.dead" checks, but nothing revalidates @tmp. After a successful return, the iterator advances to the stale @tmp, yielding either a use-after-free (if the peeled socket was closed) or a list-walk onto the new endpoint's list head (type confusion of &newep->asocs as a struct sctp_association *). Both are reachable from CapEff=0; the type-confusion path gives controlled indirect call via the outqueue.sched->init_sid pointer. Fix by re-deriving @tmp from @asoc after sctp_sendmsg_to_asoc() returns. @asoc is known to still be on ep->asocs at that point: the only callers that list_del an association from ep->asocs are sctp_association_free() (which sets asoc->base.dead) and sctp_assoc_migrate() (which changes asoc->base.sk), and sctp_wait_for_sndbuf() checks both under the lock before any successful return; a tripped check propagates as err < 0 and the loop bails before the re-derive. The SCTP_ABORT path in sctp_sendmsg_check_sflags() returns 0 and the loop hits 'continue' before sctp_sendmsg_to_asoc() is ever called, so the @tmp cached by list_for_each_entry_safe() still covers the lock-held free that ba59fb027307 ("sctp: walk the list of asoc safely") was added for. Fixes: 4910280503f3 ("sctp: add support for snd flag SCTP_SENDALL process in sendmsg") Cc: stable@vger.kernel.org Signed-off-by: Ben Morris Acked-by: Xin Long Link: https://patch.msgid.link/20260508001455.3137-1-joycathacker@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

sctp: Defer SCTP_DBG_OBJCNT_DEC() to sctp_destroy_sock().

2026-01-19T12:09:24+00:00

[ Upstream commit 622e8838a29845316668ec2e7648428878df7f9a ] SCTP_DBG_OBJCNT_INC() is called only when sctp_init_sock() returns 0 after successfully allocating sctp_sk(sk)->ep. OTOH, SCTP_DBG_OBJCNT_DEC() is called in sctp_close(). The code seems to expect that the socket is always exposed to userspace once SCTP_DBG_OBJCNT_INC() is incremented, but there is a path where the assumption is not true. In sctp_accept(), sctp_sock_migrate() could fail after sctp_init_sock(). Then, sk_common_release() does not call inet_release() nor sctp_close(). Instead, it calls sk->sk_prot->destroy(). Let's move SCTP_DBG_OBJCNT_DEC() from sctp_close() to sctp_destroy_sock(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima Acked-by: Xin Long Link: https://patch.msgid.link/20251023231751.4168390-2-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

sctp: Do not wake readers in __sctp_write_space()

2025-06-27T10:05:31+00:00

[ Upstream commit af295892a7abbf05a3c2ba7abc4d81bb448623d6 ] Function __sctp_write_space() doesn't set poll key, which leads to ep_poll_callback() waking up all waiters, not only these waiting for the socket being writable. Set the key properly using wake_up_interruptible_poll(), which is preferred over the sync variant, as writers are not woken up before at least half of the queue is available. Also, TCP does the same. Signed-off-by: Petr Malat Acked-by: Xin Long Link: https://patch.msgid.link/20250516081727.1361451-1-oss@malat.biz Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

sctp: detect and prevent references to a freed transport in sendmsg

2025-05-02T05:44:04+00:00

commit f1a69a940de58b16e8249dff26f74c8cc59b32be upstream. sctp_sendmsg() re-uses associations and transports when possible by doing a lookup based on the socket endpoint and the message destination address, and then sctp_sendmsg_to_asoc() sets the selected transport in all the message chunks to be sent. There's a possible race condition if another thread triggers the removal of that selected transport, for instance, by explicitly unbinding an address with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have been set up and before the message is sent. This can happen if the send buffer is full, during the period when the sender thread temporarily releases the socket lock in sctp_wait_for_sndbuf(). This causes the access to the transport data in sctp_outq_select_transport(), when the association outqueue is flushed, to result in a use-after-free read. This change avoids this scenario by having sctp_transport_free() signal the freeing of the transport, tagging it as "dead". In order to do this, the patch restores the "dead" bit in struct sctp_transport, which was removed in commit 47faa1e4c50e ("sctp: remove the dead field of sctp_transport"). Then, in the scenario where the sender thread has released the socket lock in sctp_wait_for_sndbuf(), the bit is checked again after re-acquiring the socket lock to detect the deletion. This is done while holding a reference to the transport to prevent it from being freed in the process. If the transport was deleted while the socket lock was relinquished, sctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the send. The bug was found by a private syzbot instance (see the error report [1] and the C reproducer that triggers it [2]). Link: https://people.igalia.com/rcn/kernel_logs/20250402__KASAN_slab-use-after-free_Read_in_sctp_outq_select_transport.txt [1] Link: https://people.igalia.com/rcn/kernel_logs/20250402__KASAN_slab-use-after-free_Read_in_sctp_outq_select_transport__repro.c [2] Cc: stable@vger.kernel.org Fixes: df132eff4638 ("sctp: clear the transport of some out_chunk_list chunks in sctp_assoc_rm_peer") Suggested-by: Xin Long Signed-off-by: Ricardo Cañuelo Navarro Acked-by: Xin Long Link: https://patch.msgid.link/20250404-kasan_slab-use-after-free_read_in_sctp_outq_select_transport__20250404-v1-1-5ce4a0b78ef2@igalia.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

sctp: ensure sk_state is set to CLOSED if hashing fails in sctp_listen_start

2024-10-17T13:11:56+00:00

[ Upstream commit 4d5c70e6155d5eae198bade4afeab3c1b15073b6 ] If hashing fails in sctp_listen_start(), the socket remains in the LISTENING state, even though it was not added to the hash table. This can lead to a scenario where a socket appears to be listening without actually being accessible. This patch ensures that if the hashing operation fails, the sk_state is set back to CLOSED before returning an error. Note that there is no need to undo the autobind operation if hashing fails, as the bind port can still be used for next listen() call on the same socket. Fixes: 76c6d988aeb3 ("sctp: add sock_reuseport for the sock in __sctp_hash_endpoint") Reported-by: Marcelo Ricardo Leitner Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller Signed-off-by: Sasha Levin

sctp: set sk_state back to CLOSED if autobind fails in sctp_listen_start

2024-10-17T13:11:21+00:00

[ Upstream commit 8beee4d8dee76b67c75dc91fd8185d91e845c160 ] In sctp_listen_start() invoked by sctp_inet_listen(), it should set the sk_state back to CLOSED if sctp_autobind() fails due to whatever reason. Otherwise, next time when calling sctp_inet_listen(), if sctp_sk(sk)->reuse is already set via setsockopt(SCTP_REUSE_PORT), sctp_sk(sk)->bind_hash will be dereferenced as sk_state is LISTENING, which causes a crash as bind_hash is NULL. KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:sctp_inet_listen+0x7f0/0xa20 net/sctp/socket.c:8617 Call Trace: __sys_listen_socket net/socket.c:1883 [inline] __sys_listen+0x1b7/0x230 net/socket.c:1894 __do_sys_listen net/socket.c:1902 [inline] Fixes: 5e8f3f703ae4 ("sctp: simplify sctp listening code") Reported-by: syzbot+f4e0f821e3a3b7cee51d@syzkaller.appspotmail.com Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Link: https://patch.msgid.link/a93e655b3c153dc8945d7a812e6d8ab0d52b7aa0.1727729391.git.lucien.xin@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

sctp: move hlist_node and hashent out of sctp_ep_common

2024-08-19T03:45:35+00:00

[ Upstream commit 3d3b2f57d4447e6e9f4096ad01d0e4129f7bc7e9 ] Struct sctp_ep_common is included in both asoc and ep, but hlist_node and hashent are only needed by ep after asoc_hashtable was dropped by Commit b5eff7128366 ("sctp: drop the old assoc hashtable of sctp"). So it is better to move hlist_node and hashent from sctp_ep_common to sctp_endpoint, and it saves some space for each asoc. Signed-off-by: Xin Long Signed-off-by: David S. Miller Stable-dep-of: 9ab0faa7f9ff ("sctp: Fix null-ptr-deref in reuseport_add_sock().") Signed-off-by: Sasha Levin

sctp: prefer struct_size over open coded arithmetic

2024-07-18T11:07:27+00:00

[ Upstream commit e5c5f3596de224422561d48eba6ece5210d967b3 ] This is an effort to get rid of all multiplications from allocation functions in order to prevent integer overflows [1][2]. As the "ids" variable is a pointer to "struct sctp_assoc_ids" and this structure ends in a flexible array: struct sctp_assoc_ids { [...] sctp_assoc_t gaids_assoc_id[]; }; the preferred way in the kernel is to use the struct_size() helper to do the arithmetic instead of the calculation "size + size * count" in the kmalloc() function. Also, refactor the code adding the "ids_size" variable to avoid sizing twice. This way, the code is more readable and safer. This code was detected with the help of Coccinelle, and audited and modified manually. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1] Link: https://github.com/KSPP/linux/issues/160 [2] Signed-off-by: Erick Archer Acked-by: Xin Long Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/PAXPR02MB724871DB78375AB06B5171C88B152@PAXPR02MB7248.eurprd02.prod.outlook.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

net: drop nopreempt requirement on sock_prot_inuse_add()

2024-07-05T07:14:08+00:00

[ Upstream commit b3cb764aa1d753cf6a58858f9e2097ba71e8100b ] This is distracting really, let's make this simpler, because many callers had to take care of this by themselves, even if on x86 this adds more code than really needed. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Stable-dep-of: a9bf9c7dc6a5 ("af_unix: Annotate data-race of sk->sk_state in unix_stream_connect().") Signed-off-by: Sasha Levin