kernel/linux.git/net/unix, branch v6.12.102

af_unix: Drop all SCM attributes for SOCKMAP.

2026-07-24T14:10:41+00:00

[ Upstream commit 965dc93481d1b80d341bdd16c27b16fe197175ee ] SOCKMAP can hide inflight fd from AF_UNIX GC. When a socket in SOCKMAP receives skb with inflight fd, sk_psock_verdict_data_ready() looks up the mapped socket and enqueue skb to its psock->ingress_skb. Since neither the old nor the new GC can inspect the psock queue, the hidden skb leaks the inflight sockets. Note that this cannot be detected via kmemleak because inflight sockets are linked to a global list. In addition, SOCKMAP redirect breaks the Tarjan-based GC's assumption that unix_edge.successor is always alive, which is no longer true once skb is redirected, resulting in use-after-free below. [0] Moreover, SOCKMAP does not call scm_stat_del() properly, so unix_show_fdinfo() could report an incorrect fd count. sk_msg_recvmsg() does not support any SCM attributes in the first place. Let's drop all SCM attributes before passing skb to the SOCKMAP layer. [0]: BUG: KASAN: slab-use-after-free in unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251) Read of size 8 at addr ffff888125362670 by task kworker/56:1/496 CPU: 56 UID: 0 PID: 496 Comm: kworker/56:1 Not tainted 7.0.0-rc7-00263-gb9d8b856689d #3 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 Workqueue: events sk_psock_backlog Call Trace: dump_stack_lvl (lib/dump_stack.c:122) print_report (mm/kasan/report.c:379) kasan_report (mm/kasan/report.c:597) unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251) unix_destroy_fpl (net/unix/garbage.c:317) unix_destruct_scm (./include/net/scm.h:80 ./include/net/scm.h:86 net/unix/af_unix.c:1976) sk_psock_backlog (./include/linux/skbuff.h:?) process_scheduled_works (kernel/workqueue.c:?) worker_thread (kernel/workqueue.c:?) kthread (kernel/kthread.c:438) ret_from_fork (arch/x86/kernel/process.c:164) ret_from_fork_asm (arch/x86/entry/entry_64.S:258) Allocated by task 955: kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78) __kasan_slab_alloc (mm/kasan/common.c:369) kmem_cache_alloc_noprof (mm/slub.c:4539) sk_prot_alloc (net/core/sock.c:2240) sk_alloc (net/core/sock.c:2301) unix_create1 (net/unix/af_unix.c:1099) unix_create (net/unix/af_unix.c:1169) __sock_create (net/socket.c:1606) __sys_socketpair (net/socket.c:1811) __x64_sys_socketpair (net/socket.c:1863 net/socket.c:1860 net/socket.c:1860) do_syscall_64 (arch/x86/entry/syscall_64.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Freed by task 496: kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78) kasan_save_free_info (mm/kasan/generic.c:587) __kasan_slab_free (mm/kasan/common.c:287) kmem_cache_free (mm/slub.c:6165) __sk_destruct (net/core/sock.c:2282 net/core/sock.c:2384) sk_psock_destroy (./include/net/sock.h:?) process_scheduled_works (kernel/workqueue.c:?) worker_thread (kernel/workqueue.c:?) kthread (kernel/kthread.c:438) ret_from_fork (arch/x86/kernel/process.c:164) ret_from_fork_asm (arch/x86/entry/entry_64.S:258) Fixes: c63829182c37 ("af_unix: Implement ->psock_update_sk_prot()") Fixes: 77462de14a43 ("af_unix: Add read_sock for stream socket types") Reported-by: Xingyu Jin Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260415184830.3988432-1-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Don't use skb_recv_datagram() in unix_stream_read_skb().

2026-07-24T14:10:41+00:00

[ Upstream commit d0aac85449dec992bb8dc2503f2cb9e94ef436db ] unix_stream_read_skb() calls skb_recv_datagram() with MSG_DONTWAIT, which is mostly equivalent to sock_error(sk) + skb_dequeue(). In the following patch, we will add a new field to cache the number of bytes in the receive queue. Then, we want to avoid introducing atomic ops in the fast path, so we will reuse the receive queue lock. As a preparation for the change, let's not use skb_recv_datagram() in unix_stream_read_skb(). Note that sock_error() is now moved out of the u->iolock mutex as the mutex does not synchronise the peer's close() at all. Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250702223606.1054680-4-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Don't check SOCK_DEAD in unix_stream_read_skb().

2026-07-24T14:10:41+00:00

[ Upstream commit 772f01049c4b722b28b3f7025b4996379f127ebf ] unix_stream_read_skb() checks SOCK_DEAD only when the dequeued skb is OOB skb. unix_stream_read_skb() is called for a SOCK_STREAM socket in SOCKMAP when data is sent to it. The function is invoked via sk_psock_verdict_data_ready(), which is set to sk->sk_data_ready(). During sendmsg(), we check if the receiver has SOCK_DEAD, so there is no point in checking it again later in ->read_skb(). Also, unix_read_skb() for SOCK_DGRAM does not have the test either. Let's remove the SOCK_DEAD test in unix_stream_read_skb(). Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250702223606.1054680-3-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Don't hold unix_state_lock() in __unix_dgram_recvmsg().

2026-07-24T14:10:41+00:00

[ Upstream commit b429a5ad19cb4efe63d18388a2a4deebcba742c6 ] When __skb_try_recv_datagram() returns NULL in __unix_dgram_recvmsg(), we hold unix_state_lock() unconditionally. This is because SOCK_SEQPACKET sk needs to return EOF in case its peer has been close()d concurrently. This behaviour totally depends on the timing of the peer's close() and reading sk->sk_shutdown, and taking the lock does not play a role. Let's drop the lock from __unix_dgram_recvmsg() and use READ_ONCE(). Signed-off-by: Kuniyuki Iwashima Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250702223606.1054680-2-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix/scm: fix whitespace errors

2026-07-24T14:10:41+00:00

[ Upstream commit 2b9996417e4ec231c91818f9ea8107ae62ef75ad ] Fix whitespace/formatting errors. Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Cc: David S. Miller Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: Simon Horman Cc: Leon Romanovsky Cc: Arnd Bergmann Cc: Christian Brauner Cc: Kuniyuki Iwashima Cc: Lennart Poettering Cc: Luca Boccassi Cc: David Rheinsberg Signed-off-by: Alexander Mikhalitsyn Link: https://lore.kernel.org/20250703222314.309967-5-aleksandr.mikhalitsyn@canonical.com Reviewed-by: Kuniyuki Iwashima Signed-off-by: Christian Brauner Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Set drop reason in unix_stream_read_skb().

2026-07-24T14:10:41+00:00

[ Upstream commit bace4b468049a558295a0f59460fcb51e28f8fde ] unix_stream_read_skb() is called when BPF SOCKMAP reads some data from a socket in the map. SOCKMAP does not support MSG_OOB, and reading OOB results in a drop. Let's set drop reasons respectively. * SOCKET_CLOSE : the socket in SOCKMAP was close()d * UNIX_SKIP_OOB : OOB was read from the socket in SOCKMAP Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250116053441.5758-7-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Set drop reason in manage_oob().

2026-07-24T14:10:41+00:00

[ Upstream commit 533643b091dd6e246d57caf81e6892fa9cbb1cc9 ] AF_UNIX SOCK_STREAM socket supports MSG_OOB. When OOB data is sent to a socket, recv() will break at that point. If the next recv() does not have MSG_OOB, the normal data following the OOB data is returned. Then, the OOB skb is dropped. Let's define a new drop reason for that case in manage_oob(). # echo 1 > /sys/kernel/tracing/events/skb/kfree_skb/enable # python3 >>> from socket import * >>> s1, s2 = socketpair(AF_UNIX) >>> s1.send(b'a', MSG_OOB) >>> s1.send(b'b') >>> s2.recv(2) b'b' # cat /sys/kernel/tracing/trace_pipe ... python3-223 ... kfree_skb: ... location=unix_stream_read_generic+0x59e/0xc20 reason: UNIX_SKIP_OOB Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250116053441.5758-6-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Set drop reason in unix_release_sock().

2026-07-24T14:10:41+00:00

[ Upstream commit c32f0bd7d4838982c6724fca0da92353f27c6f88 ] unix_release_sock() is called when the last refcnt of struct file is released. Let's define a new drop reason SKB_DROP_REASON_SOCKET_CLOSE and set it for kfree_skb() in unix_release_sock(). # echo 1 > /sys/kernel/tracing/events/skb/kfree_skb/enable # python3 >>> from socket import * >>> s1, s2 = socketpair(AF_UNIX) >>> s1.send(b'hello world') >>> s2.close() # cat /sys/kernel/tracing/trace_pipe ... python3-280 ... kfree_skb: ... protocol=0 location=unix_release_sock+0x260/0x420 reason: SOCKET_CLOSE To be precise, unix_release_sock() is also called for a new child socket in unix_stream_connect() when something fails, but the new sk does not have skb in the recv queue then and no event is logged. Note that only tcp_inbound_ao_hash() uses a similar drop reason, SKB_DROP_REASON_TCP_CLOSE, and this can be generalised later. Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250116053441.5758-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin

af_unix: Set gc_in_progress to true in unix_gc().

2026-07-04T11:43:32+00:00

[ Upstream commit d82ba05263c69fa2437fe93e4e561cc40f4c03af ] Igor Ushakov reported that unix_gc() could run with gc_in_progress being false if the work is scheduled while running: Thread 1 Thread 2 Thread 3 -------- -------- -------- unix_schedule_gc() unix_schedule_gc() `- if (!gc_in_progress) `- if (!gc_in_progress) |- gc_in_progress = true | `- queue_work() | unix_gc() <----------------/ | | |- gc_in_progress = true ... `- queue_work() | | `- gc_in_progress = false | | unix_gc() <---------------------------------------------' | ... /* gc_in_progress == false */ | `- gc_in_progress = false unix_peek_fpl() relies on gc_in_progress not to confuse GC by MSG_PEEK. Let's set gc_in_progress to true in unix_gc(). Fixes: 8b90a9f819dc ("af_unix: Run GC on only one CPU.") Reported-by: Igor Ushakov Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260501073945.1884564-1-kuniyu@google.com Signed-off-by: Jakub Kicinski [ Add setting gc_in_progress in __unix_gc(). Keep the existing set in unix_gc() for wait_for_unix_gc() over-limit throttling. ] Signed-off-by: Igor Ushakov Signed-off-by: Sasha Levin

af_unix: Fix UAF read of tail->len in unix_stream_data_wait()

2026-06-01T15:46:20+00:00

commit be309f8eae8b474a4a617eaae01324da996fc719 upstream. unix_stream_data_wait() does skb_peek_tail(&sk->sk_receive_queue) without holding any lock that prevents SKBs on that queue from being dequeued and freed. This has been the case since commit 79f632c71bea ("unix/stream: fix peeking with an offset larger than data in queue"). The first consequence of this is that the pointer comparison `tail != last` can be false even if `last` semantically refers to an already-freed SKB while `tail` is a new SKB allocated at the same address; which can cause unix_stream_data_wait() to wrongly keep blocking after new data has arrived, but only in a weird scenario where a peeking recv() and a normal recv() on the same socket are racing, which is probably not a real problem. But since commit 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix sockets"), `tail` is actually dereferenced, which can cause UAF in the following race scenario (where test_setup() runs single-threaded, and afterwards, test_thread1() and test_thread2() run concurrently in two threads: ``` static int socks[2]; void test_setup(void) { socketpair(AF_UNIX, SOCK_STREAM, 0, socks); send(socks[1], "A", 1, 0); int peekoff = 1; setsockopt(socks[0], SOL_SOCKET, SO_PEEK_OFF, &peekoff, sizeof(peekoff)); } void test_thread1(void) { char dummy; recv(socks[0], &dummy, 1, MSG_PEEK); } void test_thread2(void) { char dummy; recv(socks[0], &dummy, 1, 0); shutdown(socks[1], SHUT_WR); } ``` when racing like this: ``` thread1 thread2 unix_stream_read_generic mutex_lock(&u->iolock) skb_peek(&sk->sk_receive_queue) skb_peek_next(skb, &sk->sk_receive_queue) mutex_unlock(&u->iolock) unix_stream_read_generic unix_state_lock(sk) skb_peek(&sk->sk_receive_queue) unix_state_unlock(sk) unix_stream_data_wait unix_state_lock(sk) tail = skb_peek_tail(&sk->sk_receive_queue) spin_lock(&sk->sk_receive_queue.lock) __skb_unlink(skb, &sk->sk_receive_queue) spin_unlock(&sk->sk_receive_queue.lock) consume_skb(skb) [frees the SKB] `tail != last`: false `tail`: true `tail->len != last_len` ***UAF*** ``` Fix the UAF by removing the read of tail->len; checking tail->len would only make sense if SKBs in the receive queue of a UNIX socket could grow, which can no longer happen. Kuniyuki explained: > When commit 869e7c62486e ("net: af_unix: implement stream sendpage > support") added sendpage() support, data could be appended to the last > skb in the receiver's queue. > > That's why we needed to check if the length of the last skb was changed > while waiting for new data in unix_stream_data_wait(). > > However, commit a0dbf5f818f9 ("af_unix: Support MSG_SPLICE_PAGES") and > commit 57d44a354a43 ("unix: Convert unix_stream_sendpage() to use > MSG_SPLICE_PAGES") refactored sendmsg(), and now data is always added > to a new skb. That means this fix is not suitable for kernels before 6.5. Fixes: 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix sockets") Cc: stable@vger.kernel.org # 6.5.x Signed-off-by: Jann Horn Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260518-b4-unix-recv-wait-hotfix-v2-1-83e29ce8ad31@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman