[v6.1] inconsistent lock state in __sk_receive_skb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=177e0836580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=44f0626dd6284f02663c
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+44f062...@syzkaller.appspotmail.com

================================
WARNING: inconsistent lock state
syzkaller #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
syz.4.325/5772 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff0000e9d08d30 (slock-AF_PHONET/1){+.?.}-{2:2}, at: __sk_receive_skb+0x154/0x850 net/core/sock.c:560
{SOFTIRQ-ON-W} state was registered at:
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
_raw_spin_lock_nested+0x5c/0x78 kernel/locking/spinlock.c:378
__sk_receive_skb+0x154/0x850 net/core/sock.c:560
sk_receive_skb include/net/sock.h:2097 [inline]
pep_do_rcv+0x4b4/0x758 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1138 [inline]
__release_sock+0x1b4/0x3b4 net/core/sock.c:2945
release_sock+0x60/0x1bc net/core/sock.c:3511
pep_sock_accept+0xc7c/0x1360 net/phonet/pep.c:879
pn_socket_accept+0x120/0x2dc net/phonet/socket.c:304
do_accept+0x448/0x5fc net/socket.c:1890
__sys_accept4_file net/socket.c:1931 [inline]
__sys_accept4+0xb4/0x12c net/socket.c:1961
__do_sys_accept4 net/socket.c:1972 [inline]
__se_sys_accept4 net/socket.c:1969 [inline]
__arm64_sys_accept4+0x9c/0xb8 net/socket.c:1969
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 148
hardirqs last enabled at (148): [<ffff800011b23ea4>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
hardirqs last enabled at (148): [<ffff800011b23ea4>] _raw_spin_unlock_irq+0x3c/0x90 kernel/locking/spinlock.c:202
hardirqs last disabled at (147): [<ffff800011b23c68>] __raw_spin_lock_irq include/linux/spinlock_api_smp.h:117 [inline]
hardirqs last disabled at (147): [<ffff800011b23c68>] _raw_spin_lock_irq+0x34/0x98 kernel/locking/spinlock.c:170
softirqs last enabled at (142): [<ffff80000fdd29c8>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (143): [<ffff800008020164>] __do_softirq+0x14/0x20 kernel/softirq.c:630

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(slock-AF_PHONET/1);
<Interrupt>
lock(slock-AF_PHONET/1);

*** DEADLOCK ***

4 locks held by syz.4.325/5772:
#0: ffff0000e9d08770 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
#0: ffff0000e9d08770 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: pep_sendmsg+0x5d4/0x8ac net/phonet/pep.c:1199
#1: ffff8000153f72c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:349
#2: ffff0000e9d080b0 (slock-AF_PHONET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
#2: ffff0000e9d080b0 (slock-AF_PHONET){+.-.}-{2:2}, at: __sk_receive_skb+0x164/0x850 net/core/sock.c:562
#3: ffff0000e9d08130 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2097 [inline]
#3: ffff0000e9d08130 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x600/0xa4c net/phonet/af_phonet.c:-1

stack backtrace:
CPU: 0 PID: 5772 Comm: syz.4.325 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call trace:
dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
dump_stack+0x1c/0x5c lib/dump_stack.c:113
print_usage_bug+0x4c0/0x6d8 kernel/locking/lockdep.c:3957
valid_state kernel/locking/lockdep.c:3969 [inline]
mark_lock_irq+0x850/0xab0 kernel/locking/lockdep.c:-1
mark_lock+0x224/0x320 kernel/locking/lockdep.c:4628
mark_usage kernel/locking/lockdep.c:-1 [inline]
__lock_acquire+0xa78/0x6800 kernel/locking/lockdep.c:5003
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
_raw_spin_lock_nested+0x5c/0x78 kernel/locking/spinlock.c:378
__sk_receive_skb+0x154/0x850 net/core/sock.c:560
sk_receive_skb include/net/sock.h:2097 [inline]
pep_do_rcv+0x4b4/0x758 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1138 [inline]
__sk_receive_skb+0x3d0/0x850 net/core/sock.c:569
sk_receive_skb include/net/sock.h:2097 [inline]
phonet_rcv+0x600/0xa4c net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:5619 [inline]
__netif_receive_skb+0xcc/0x2a8 net/core/dev.c:5733
process_backlog+0x408/0x710 net/core/dev.c:6061
__napi_poll+0xb4/0x3f0 net/core/dev.c:6628
napi_poll net/core/dev.c:6695 [inline]
net_rx_action+0x514/0xb18 net/core/dev.c:6809
handle_softirqs+0x318/0xc60 kernel/softirq.c:596
__do_softirq+0x14/0x20 kernel/softirq.c:630
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:80
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:897
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:85
do_softirq+0xf8/0x1a8 kernel/softirq.c:497
__local_bh_enable_ip+0x250/0x37c kernel/softirq.c:421
local_bh_enable+0x28/0x34 include/linux/bottom_half.h:33
netif_rx+0xa4/0xc4 net/core/dev.c:5140
pn_send+0x454/0x6d8 net/phonet/af_phonet.c:185
pn_skb_send+0x1dc/0x50c net/phonet/af_phonet.c:272
pipe_skb_send+0x274/0x470 net/phonet/pep.c:1130
pep_sendmsg+0x810/0x8ac net/phonet/pep.c:1206
pn_socket_sendmsg+0x1a4/0x214 net/phonet/socket.c:425
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
sock_write_iter+0x268/0x360 net/socket.c:1143
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x3ec/0x7f0 fs/read_write.c:584
ksys_write+0x12c/0x224 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1136ef16580000

kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=44f0626dd6284f02663c
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13fd0836580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=117954ce580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/edc1e2feca67/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=16ad42d2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+44f062...@syzkaller.appspotmail.com

================================
WARNING: inconsistent lock state
syzkaller #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.

ksoftirqd/0/15 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff0000d0a11ff0 (slock-AF_PHONET/1){+.?.}-{2:2}, at: __sk_receive_skb+0x154/0x850 net/core/sock.c:560

{SOFTIRQ-ON-W} state was registered at:
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
_raw_spin_lock_nested+0x5c/0x78 kernel/locking/spinlock.c:378
__sk_receive_skb+0x154/0x850 net/core/sock.c:560
sk_receive_skb include/net/sock.h:2097 [inline]
pep_do_rcv+0x4b4/0x758 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1138 [inline]
__release_sock+0x1b4/0x3b4 net/core/sock.c:2945
release_sock+0x60/0x1bc net/core/sock.c:3511
pep_sock_accept+0xc7c/0x1360 net/phonet/pep.c:879
pn_socket_accept+0x120/0x2dc net/phonet/socket.c:304
do_accept+0x448/0x5fc net/socket.c:1890
__sys_accept4_file net/socket.c:1931 [inline]
__sys_accept4+0xb4/0x12c net/socket.c:1961
__do_sys_accept4 net/socket.c:1972 [inline]
__se_sys_accept4 net/socket.c:1969 [inline]
__arm64_sys_accept4+0x9c/0xb8 net/socket.c:1969
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

irq event stamp: 484448
hardirqs last enabled at (484448): [<ffff800011b23ea4>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
hardirqs last enabled at (484448): [<ffff800011b23ea4>] _raw_spin_unlock_irq+0x3c/0x90 kernel/locking/spinlock.c:202
hardirqs last disabled at (484447): [<ffff800011b23c68>] __raw_spin_lock_irq include/linux/spinlock_api_smp.h:117 [inline]
hardirqs last disabled at (484447): [<ffff800011b23c68>] _raw_spin_lock_irq+0x34/0x98 kernel/locking/spinlock.c:170
softirqs last enabled at (484376): [<ffff8000081ac394>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last enabled at (484376): [<ffff8000081ac394>] handle_softirqs+0xaec/0xc60 kernel/softirq.c:624
softirqs last disabled at (484381): [<ffff8000081af30c>] run_ksoftirqd+0x7c/0x2ac kernel/softirq.c:968

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(slock-AF_PHONET/1);
<Interrupt>
lock(slock-AF_PHONET/1);

*** DEADLOCK ***

3 locks held by ksoftirqd/0/15:
#0: ffff8000153f72c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:349
#1: ffff0000f1199ff0 (slock-AF_PHONET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
#1: ffff0000f1199ff0 (slock-AF_PHONET){+.-.}-{2:2}, at: __sk_receive_skb+0x164/0x850 net/core/sock.c:562
#2: ffff0000f119a070 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2097 [inline]
#2: ffff0000f119a070 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x600/0xa4c net/phonet/af_phonet.c:-1

stack backtrace:
CPU: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0

run_ksoftirqd+0x7c/0x2ac kernel/softirq.c:968
smpboot_thread_fn+0x4b0/0x964 kernel/smpboot.c:164
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850


---
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