INFO: task hung in tcp_sendmsg

Status: premoderation: reported on 2026/09/15 07:42
Reported-by: syzbot+1e7796b74913a0423dc7@syzkaller.appspotmail.com
First crash: 5d01h, last: 5d01h

Sample crash report:
INFO: task syz.0.120:674 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.120       state:D stack:0     pid:674   tgid:671   ppid:293    flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6063 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7883
 __schedule_loop kernel/sched/core.c:7960 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7975
 __lock_sock net/core/sock.c:3088 [inline]
 lock_sock_nested+0x17e/0x2a0 net/core/sock.c:3670
 lock_sock include/net/sock.h:1678 [inline]
 sk_stream_wait_memory+0x905/0xf80 net/core/stream.c:145
 tcp_sendmsg_locked+0x134c/0x4ac0 net/ipv4/tcp.c:1322
 tcp_sendmsg+0x3e/0xd0 net/ipv4/tcp.c:1365
 inet_sendmsg+0xb7/0x120 net/ipv4/af_inet.c:858
 sock_sendmsg_nosec net/socket.c:713 [inline]
 __sock_sendmsg net/socket.c:727 [inline]
 __sys_sendto+0x5d8/0x6e0 net/socket.c:2197
 __do_sys_sendto net/socket.c:2204 [inline]
 __se_sys_sendto net/socket.c:2200 [inline]
 __x64_sys_sendto+0xe9/0x100 net/socket.c:2200
 x64_sys_call+0x2c2c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fe8a299e159
RSP: 002b:00007fe8a37a0028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fe8a2c25fa0 RCX: 00007fe8a299e159
RDX: ffffffffffffff94 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007fe8a2a3503b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe8a2c26038 R14: 00007fe8a2c25fa0 R15: 00007ffe4c1f9c48
 </TASK>
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 f62b9527b829eee6a2ac5cf651ba087b59645d0c
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xe45/0xf90 kernel/hung_task.c:423
 kthread+0x2c4/0x360 kernel/kthread.c:389
 ret_from_fork+0x64/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 17 Comm: ksoftirqd/0 Not tainted syzkaller #0 f62b9527b829eee6a2ac5cf651ba087b59645d0c
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:clear_page_erms+0xb/0x30 arch/x86/lib/clear_page_64.S:50
Code: 48 8d 7f 40 75 d9 90 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa b9 00 10 00 00 31 c0 <f3> aa e9 8e 7c 03 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000116dd8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff92000022dc0 RCX: 0000000000000f40
RDX: ffff88813f37d000 RSI: 0000000000000001 RDI: ffff88813f37d0c0
RBP: ffffc90000116e90 R08: ffffffff87e4667f R09: 0000000000000000
R10: ffffed1027e6fa00 R11: fffffbfff0fc8cd0 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc9c1dae4c0 CR3: 000000010af0c000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 prep_new_page+0x2d/0x180 mm/page_alloc.c:1871
 get_page_from_freelist+0x4aea/0x4ba0 mm/page_alloc.c:3948
 __alloc_pages_noprof+0x35a/0x7e0 mm/page_alloc.c:5315
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x430 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x591/0x8c0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4239 [inline]
 kmem_cache_alloc_noprof+0x290/0x410 mm/slub.c:4260
 skb_clone+0x21d/0x470 net/core/skbuff.c:2084
 deliver_clone net/bridge/br_forward.c:125 [inline]
 br_flood+0x650/0x720 net/bridge/br_forward.c:246
 br_handle_frame_finish+0x1157/0x1620 net/bridge/br_input.c:215
 nf_hook_bridge_pre net/bridge/br_input.c:301 [inline]
 br_handle_frame+0x5a5/0xba0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xfc1/0x3a70 net/core/dev.c:5695
 __netif_receive_skb_one_core net/core/dev.c:5799 [inline]
 __netif_receive_skb net/core/dev.c:5914 [inline]
 process_backlog+0x40b/0xaf0 net/core/dev.c:6250
 __napi_poll+0xd0/0x600 net/core/dev.c:6901
 napi_poll net/core/dev.c:6970 [inline]
 net_rx_action+0x5dc/0xd70 net/core/dev.c:7092
 handle_softirqs+0x1aa/0x620 kernel/softirq.c:621
 run_ksoftirqd+0x20/0x30 kernel/softirq.c:999
 smpboot_thread_fn+0x486/0x8b0 kernel/smpboot.c:164
 kthread+0x2c4/0x360 kernel/kthread.c:389
 ret_from_fork+0x64/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
net_ratelimit: 135636 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:92:4e:7c:3c:8b:b3, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:92:4e:7c:3c:8b:b3, vlan:0)
net_ratelimit: 156714 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:92:4e:7c:3c:8b:b3, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/15 07:41 android16-6.12 8929b56bce67 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in tcp_sendmsg
* Struck through repros no longer work on HEAD.