kernel/linux.git/net/core/skmsg.c, branch v7.0-rc7

bpf: sockmap: Fix use-after-free of sk->sk_socket in sk_psock_verdict_data_ready().

2026-04-02T01:54:04+00:00

syzbot reported use-after-free of AF_UNIX socket's sk->sk_socket in sk_psock_verdict_data_ready(). [0] In unix_stream_sendmsg(), the peer socket's ->sk_data_ready() is called after dropping its unix_state_lock(). Although the sender socket holds the peer's refcount, it does not prevent the peer's sock_orphan(), and the peer's sk_socket might be freed after one RCU grace period. Let's fetch the peer's sk->sk_socket and sk->sk_socket->ops under RCU in sk_psock_verdict_data_ready(). [0]: BUG: KASAN: slab-use-after-free in sk_psock_verdict_data_ready+0xec/0x590 net/core/skmsg.c:1278 Read of size 8 at addr ffff8880594da860 by task syz.4.1842/11013 CPU: 1 UID: 0 PID: 11013 Comm: syz.4.1842 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 sk_psock_verdict_data_ready+0xec/0x590 net/core/skmsg.c:1278 unix_stream_sendmsg+0x8a3/0xe80 net/unix/af_unix.c:2482 sock_sendmsg_nosec net/socket.c:721 [inline] __sock_sendmsg net/socket.c:736 [inline] ____sys_sendmsg+0x972/0x9f0 net/socket.c:2585 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2639 __sys_sendmsg net/socket.c:2671 [inline] __do_sys_sendmsg net/socket.c:2676 [inline] __se_sys_sendmsg net/socket.c:2674 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2674 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7facf899c819 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007facf9827028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007facf8c15fa0 RCX: 00007facf899c819 RDX: 0000000000000000 RSI: 0000200000000500 RDI: 0000000000000004 RBP: 00007facf8a32c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007facf8c16038 R14: 00007facf8c15fa0 R15: 00007ffd41b01c78 Allocated by task 11013: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4538 [inline] slab_alloc_node mm/slub.c:4866 [inline] kmem_cache_alloc_lru_noprof+0x2b8/0x640 mm/slub.c:4885 sock_alloc_inode+0x28/0xc0 net/socket.c:316 alloc_inode+0x6a/0x1b0 fs/inode.c:347 new_inode_pseudo include/linux/fs.h:3003 [inline] sock_alloc net/socket.c:631 [inline] __sock_create+0x12d/0x9d0 net/socket.c:1562 sock_create net/socket.c:1656 [inline] __sys_socketpair+0x1c4/0x560 net/socket.c:1803 __do_sys_socketpair net/socket.c:1856 [inline] __se_sys_socketpair net/socket.c:1853 [inline] __x64_sys_socketpair+0x9b/0xb0 net/socket.c:1853 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 15: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2685 [inline] slab_free mm/slub.c:6165 [inline] kmem_cache_free+0x187/0x630 mm/slub.c:6295 rcu_do_batch kernel/rcu/tree.c:2617 [inline] rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869 handle_softirqs+0x22a/0x870 kernel/softirq.c:622 run_ksoftirqd+0x36/0x60 kernel/softirq.c:1063 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Fixes: c63829182c37 ("af_unix: Implement ->psock_update_sk_prot()") Closes: https://lore.kernel.org/bpf/69cc6b9f.a70a0220.128fd0.004b.GAE@google.com/ Reported-by: syzbot+2184232f07e3677fbaef@syzkaller.appspotmail.com Signed-off-by: Kuniyuki Iwashima Signed-off-by: Martin KaFai Lau Reviewed-by: Jiayuan Chen Link: https://patch.msgid.link/20260401005418.2452999-1-kuniyu@google.com

net: annotate data-races around sk->sk_{data_ready,write_space}

2026-02-27T03:23:03+00:00

skmsg (and probably other layers) are changing these pointers while other cpus might read them concurrently. Add corresponding READ_ONCE()/WRITE_ONCE() annotations for UDP, TCP and AF_UNIX. Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Reported-by: syzbot+87f770387a9e5dc6b79b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/699ee9fc.050a0220.1cd54b.0009.GAE@google.com/ Signed-off-by: Eric Dumazet Cc: Daniel Borkmann Cc: John Fastabend Cc: Jakub Sitnicki Cc: Willem de Bruijn Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260225131547.1085509-1-edumazet@google.com Signed-off-by: Jakub Kicinski

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

bpf, sockmap: Fix FIONREAD for sockmap

2026-01-27T17:11:30+00:00

A socket using sockmap has its own independent receive queue: ingress_msg. This queue may contain data from its own protocol stack or from other sockets. Therefore, for sockmap, relying solely on copied_seq and rcv_nxt to calculate FIONREAD is not enough. This patch adds a new msg_tot_len field in the psock structure to record the data length in ingress_msg. Additionally, we implement new ioctl interfaces for TCP and UDP to intercept FIONREAD operations. Note that we intentionally do not include sk_receive_queue data in the FIONREAD result. Data in sk_receive_queue has not yet been processed by the BPF verdict program, and may be redirected to other sockets or dropped. Including it would create semantic ambiguity since this data may never be readable by the user. Unix and VSOCK sockets have similar issues, but fixing them is outside the scope of this patch as it would require more intrusive changes. Previous work by John Fastabend made some efforts towards FIONREAD support: commit e5c6de5fa025 ("bpf, sockmap: Incorrectly handling copied_seq") Although the current patch is based on the previous work by John Fastabend, it is acceptable for our Fixes tag to point to the same commit. FD1:read() -- FD1->copied_seq++ | [read data] | [enqueue data] v [sockmap] -> ingress to self -> ingress_msg queue FD1 native stack ------> ^ -- FD1->rcv_nxt++ -> redirect to other | [enqueue data] | | | ingress to FD1 v ^ ... | [sockmap] FD2 native stack Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()") Signed-off-by: Jiayuan Chen Reviewed-by: Jakub Sitnicki Link: https://lore.kernel.org/r/20260124113314.113584-3-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov

bpf, sockmap: Fix incorrect copied_seq calculation

2026-01-27T17:11:30+00:00

A socket using sockmap has its own independent receive queue: ingress_msg. This queue may contain data from its own protocol stack or from other sockets. The issue is that when reading from ingress_msg, we update tp->copied_seq by default. However, if the data is not from its own protocol stack, tcp->rcv_nxt is not increased. Later, if we convert this socket to a native socket, reading from this socket may fail because copied_seq might be significantly larger than rcv_nxt. This fix also addresses the syzkaller-reported bug referenced in the Closes tag. This patch marks the skmsg objects in ingress_msg. When reading, we update copied_seq only if the data is from its own protocol stack. FD1:read() -- FD1->copied_seq++ | [read data] | [enqueue data] v [sockmap] -> ingress to self -> ingress_msg queue FD1 native stack ------> ^ -- FD1->rcv_nxt++ -> redirect to other | [enqueue data] | | | ingress to FD1 v ^ ... | [sockmap] FD2 native stack Closes: https://syzkaller.appspot.com/bug?extid=06dbd397158ec0ea4983 Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()") Reviewed-by: Jakub Sitnicki Reviewed-by: John Fastabend Signed-off-by: Jiayuan Chen Link: https://lore.kernel.org/r/20260124113314.113584-2-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov

net: replace use of system_wq with system_percpu_wq

2025-09-23T00:40:30+00:00

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. system_unbound_wq should be the default workqueue so as not to enforce locality constraints for random work whenever it's not required. Adding system_dfl_wq to encourage its use when unbound work should be used. The old system_unbound_wq will be kept for a few release cycles. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Link: https://patch.msgid.link/20250918142427.309519-3-marco.crivellari@suse.com Signed-off-by: Jakub Kicinski

bpf, sockmap: Fix psock incorrectly pointing to sk

2025-06-10T16:16:15+00:00

We observed an issue from the latest selftest: sockmap_redir where sk_psock(psock->sk) != psock in the backlog. The root cause is the special behavior in sockmap_redir - it frequently performs map_update() and map_delete() on the same socket. During map_update(), we create a new psock and during map_delete(), we eventually free the psock via rcu_work in sk_psock_drop(). However, pending workqueues might still exist and not be processed yet. If users immediately perform another map_update(), a new psock will be allocated for the same sk, resulting in two psocks pointing to the same sk. When the pending workqueue is later triggered, it uses the old psock to access sk for I/O operations, which is incorrect. Timing Diagram: cpu0 cpu1 map_update(sk): sk->psock = psock1 psock1->sk = sk map_delete(sk): rcu_work_free(psock1) map_update(sk): sk->psock = psock2 psock2->sk = sk workqueue: wakeup with psock1, but the sk of psock1 doesn't belong to psock1 rcu_handler: clean psock1 free(psock1) Previously, we used reference counting to address the concurrency issue between backlog and sock_map_close(). This logic remains necessary as it prevents the sk from being freed while processing the backlog. But this patch prevents pending backlogs from using a psock after it has been stopped. Note: We cannot call cancel_delayed_work_sync() in map_delete() since this might be invoked in BPF context by BPF helper, and the function may sleep. Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Signed-off-by: Jiayuan Chen Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Link: https://lore.kernel.org/bpf/20250609025908.79331-1-jiayuan.chen@linux.dev

bpf, sockmap: Avoid using sk_socket after free when sending

2025-05-22T23:16:37+00:00

The sk->sk_socket is not locked or referenced in backlog thread, and during the call to skb_send_sock(), there is a race condition with the release of sk_socket. All types of sockets(tcp/udp/unix/vsock) will be affected. Race conditions: ''' CPU0 CPU1 backlog::skb_send_sock sendmsg_unlocked sock_sendmsg sock_sendmsg_nosec close(fd): ... ops->release() -> sock_map_close() sk_socket->ops = NULL free(socket) sock->ops->sendmsg ^ panic here ''' The ref of psock become 0 after sock_map_close() executed. ''' void sock_map_close() { ... if (likely(psock)) { ... // !! here we remove psock and the ref of psock become 0 sock_map_remove_links(sk, psock) psock = sk_psock_get(sk); if (unlikely(!psock)) goto no_psock; <=== Control jumps here via goto ... cancel_delayed_work_sync(&psock->work); <=== not executed sk_psock_put(sk, psock); ... } ''' Based on the fact that we already wait for the workqueue to finish in sock_map_close() if psock is held, we simply increase the psock reference count to avoid race conditions. With this patch, if the backlog thread is running, sock_map_close() will wait for the backlog thread to complete and cancel all pending work. If no backlog running, any pending work that hasn't started by then will fail when invoked by sk_psock_get(), as the psock reference count have been zeroed, and sk_psock_drop() will cancel all jobs via cancel_delayed_work_sync(). In summary, we require synchronization to coordinate the backlog thread and close() thread. The panic I catched: ''' Workqueue: events sk_psock_backlog RIP: 0010:sock_sendmsg+0x21d/0x440 RAX: 0000000000000000 RBX: ffffc9000521fad8 RCX: 0000000000000001 ... Call Trace: ? die_addr+0x40/0xa0 ? exc_general_protection+0x14c/0x230 ? asm_exc_general_protection+0x26/0x30 ? sock_sendmsg+0x21d/0x440 ? sock_sendmsg+0x3e0/0x440 ? __pfx_sock_sendmsg+0x10/0x10 __skb_send_sock+0x543/0xb70 sk_psock_backlog+0x247/0xb80 ... ''' Fixes: 4b4647add7d3 ("sock_map: avoid race between sock_map_close and sk_psock_put") Reported-by: Michal Luczaj Signed-off-by: Jiayuan Chen Signed-off-by: Martin KaFai Lau Reviewed-by: John Fastabend Link: https://lore.kernel.org/r/20250516141713.291150-1-jiayuan.chen@linux.dev

bpf, sockmap: Fix panic when calling skb_linearize

2025-04-10T02:59:00+00:00

The panic can be reproduced by executing the command: ./bench sockmap -c 2 -p 1 -a --rx-verdict-ingress --rx-strp 100000 Then a kernel panic was captured: ''' [ 657.460555] kernel BUG at net/core/skbuff.c:2178! [ 657.462680] Tainted: [W]=WARN [ 657.463287] Workqueue: events sk_psock_backlog ... [ 657.469610] [ 657.469738] ? die+0x36/0x90 [ 657.469916] ? do_trap+0x1d0/0x270 [ 657.470118] ? pskb_expand_head+0x612/0xf40 [ 657.470376] ? pskb_expand_head+0x612/0xf40 [ 657.470620] ? do_error_trap+0xa3/0x170 [ 657.470846] ? pskb_expand_head+0x612/0xf40 [ 657.471092] ? handle_invalid_op+0x2c/0x40 [ 657.471335] ? pskb_expand_head+0x612/0xf40 [ 657.471579] ? exc_invalid_op+0x2d/0x40 [ 657.471805] ? asm_exc_invalid_op+0x1a/0x20 [ 657.472052] ? pskb_expand_head+0xd1/0xf40 [ 657.472292] ? pskb_expand_head+0x612/0xf40 [ 657.472540] ? lock_acquire+0x18f/0x4e0 [ 657.472766] ? find_held_lock+0x2d/0x110 [ 657.472999] ? __pfx_pskb_expand_head+0x10/0x10 [ 657.473263] ? __kmalloc_cache_noprof+0x5b/0x470 [ 657.473537] ? __pfx___lock_release.isra.0+0x10/0x10 [ 657.473826] __pskb_pull_tail+0xfd/0x1d20 [ 657.474062] ? __kasan_slab_alloc+0x4e/0x90 [ 657.474707] sk_psock_skb_ingress_enqueue+0x3bf/0x510 [ 657.475392] ? __kasan_kmalloc+0xaa/0xb0 [ 657.476010] sk_psock_backlog+0x5cf/0xd70 [ 657.476637] process_one_work+0x858/0x1a20 ''' The panic originates from the assertion BUG_ON(skb_shared(skb)) in skb_linearize(). A previous commit(see Fixes tag) introduced skb_get() to avoid race conditions between skb operations in the backlog and skb release in the recvmsg path. However, this caused the panic to always occur when skb_linearize is executed. The "--rx-strp 100000" parameter forces the RX path to use the strparser module which aggregates data until it reaches 100KB before calling sockmap logic. The 100KB payload exceeds MAX_MSG_FRAGS, triggering skb_linearize. To fix this issue, just move skb_get into sk_psock_skb_ingress_enqueue. ''' sk_psock_backlog: sk_psock_handle_skb skb_get(skb) <== we move it into 'sk_psock_skb_ingress_enqueue' sk_psock_skb_ingress____________ ↓ | | → sk_psock_skb_ingress_self | sk_psock_skb_ingress_enqueue sk_psock_verdict_apply_________________↑ skb_linearize ''' Note that for verdict_apply path, the skb_get operation is unnecessary so we add 'take_ref' param to control it's behavior. Fixes: a454d84ee20b ("bpf, sockmap: Fix skb refcnt race after locking changes") Signed-off-by: Jiayuan Chen Link: https://lore.kernel.org/r/20250407142234.47591-4-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov

bpf, sockmap: fix duplicated data transmission

2025-04-10T02:58:59+00:00

In the !ingress path under sk_psock_handle_skb(), when sending data to the remote under snd_buf limitations, partial skb data might be transmitted. Although we preserved the partial transmission state (offset/length), the state wasn't properly consumed during retries. This caused the retry path to resend the entire skb data instead of continuing from the previous offset, resulting in data overlap at the receiver side. Fixes: 405df89dd52c ("bpf, sockmap: Improved check for empty queue") Signed-off-by: Jiayuan Chen Link: https://lore.kernel.org/r/20250407142234.47591-3-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov