[syzbot] [net?] kernel BUG in pn_socket_sendmsg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 97e797263a5e Add linux-next specific files for 20260420
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=111f5702580000
kernel config: https://syzkaller.appspot.com/x/.config?x=354b135d724a721f
dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14bbf4ce580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152051ba580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfe08255b02b/disk-97e79726.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70874e341331/vmlinux-97e79726.xz
kernel image: https://storage.googleapis.com/syzbot-assets/68352f7fca94/bzImage-97e79726.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+706f5e...@syzkaller.appspotmail.com

netlink: 'syz.0.17': attribute type 2 has an invalid length.
------------[ cut here ]------------
kernel BUG at net/phonet/socket.c:213!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 6014 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
RIP: 0010:pn_socket_sendmsg+0x240/0x250 net/phonet/socket.c:421
Code: cc cc cc e8 c2 0c d2 00 89 d9 80 e1 07 fe c1 38 c1 0f 8c 04 ff ff ff 48 89 df e8 bb d3 be f7 e9 f7 fe ff ff e8 c1 5a 55 f7 90 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90
RSP: 0018:ffffc900050d7ba0 EFLAGS: 00010293
RAX: ffffffff8a6fa75f RBX: 0000000000000000 RCX: ffff888031b91ec0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900050d7c58 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f9e8df R12: dffffc0000000000
R13: ffff88805c7b5ec0 R14: ffff888034fecec0 R15: 1ffff92000a1af78
FS: 00007f347ac666c0(0000) GS:ffff888125a62000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f347b5f7680 CR3: 000000003d362000 CR4: 00000000003526f0
Call Trace:
<TASK>
sock_sendmsg_nosec+0x112/0x150 net/socket.c:797
__sock_sendmsg net/socket.c:812 [inline]
__sys_sendto+0x402/0x590 net/socket.c:2280
__do_sys_sendto net/socket.c:2287 [inline]
__se_sys_sendto net/socket.c:2283 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2283
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f347b5cd04e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f347ac64e88 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f347ac666c0 RCX: 00007f347b5cd04e
RDX: 0000000000000020 RSI: 00007f347ac65000 RDI: 0000000000000006
RBP: 0000000000000000 R08: 00007f347ac64f04 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
R13: 00007f347ac64f58 R14: 00007f347ac65000 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
RIP: 0010:pn_socket_sendmsg+0x240/0x250 net/phonet/socket.c:421
Code: cc cc cc e8 c2 0c d2 00 89 d9 80 e1 07 fe c1 38 c1 0f 8c 04 ff ff ff 48 89 df e8 bb d3 be f7 e9 f7 fe ff ff e8 c1 5a 55 f7 90 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90
RSP: 0018:ffffc900050d7ba0 EFLAGS: 00010293
RAX: ffffffff8a6fa75f RBX: 0000000000000000 RCX: ffff888031b91ec0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900050d7c58 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f9e8df R12: dffffc0000000000
R13: ffff88805c7b5ec0 R14: ffff888034fecec0 R15: 1ffff92000a1af78
FS: 00007f347ac666c0(0000) GS:ffff888125a62000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f347b5f7680 CR3: 000000003d362000 CR4: 00000000003526f0


---
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[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] net: phonet: fix BUG_ON() in pn_socket_autobind()
Author: karti...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master

pn_socket_autobind() calls pn_socket_bind() and treats
-EINVAL as a signal that the socket was already bound,
then uses BUG_ON() to verify it:

if (err != -EINVAL)
return err;
BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));

However, pn_socket_bind() returns -EINVAL in multiple
cases:

1. address length too short
2. socket not in TCP_CLOSE state
3. socket already bound <- only intended case

When -EINVAL comes from cases 1 or 2, sobject is still
zero (never assigned), causing BUG_ON to fire and crash
the kernel.

Fix this by checking the bound state directly via
pn_port(sobject) BEFORE calling pn_socket_bind(),
eliminating the ambiguous -EINVAL interpretation
entirely.

Reported-by: syzbot+706f5e...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---
net/phonet/socket.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/phonet/socket.c b/net/phonet/socket.c
index c4af26357144..5a55e7d14e85 100644
--- a/net/phonet/socket.c
+++ b/net/phonet/socket.c
@@ -204,14 +204,14 @@ static int pn_socket_autobind(struct socket *sock)
struct sockaddr_pn sa;
int err;

+ if (pn_port(pn_sk(sock->sk)->sobject))
+ return 0; /* socket was already bound */
+
memset(&sa, 0, sizeof(sa));
sa.spn_family = AF_PHONET;
err = pn_socket_bind(sock, (struct sockaddr_unsized *)&sa,
sizeof(struct sockaddr_pn));
- if (err != -EINVAL)
- return err;
- BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));
- return 0; /* socket was already bound */
+ return err;
}

static int pn_socket_connect(struct socket *sock, struct sockaddr_unsized *addr,
--
2.43.0

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] net: phonet: fix BUG_ON() in pn_socket_autobind()
Author: karti...@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __sk_receive_skb

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor220/8545 is trying to acquire lock:
ffff88803ef5ae60 (slock-AF_PHONET/1){+.+.}-{3:3}, at: __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563

but task is already holding lock:
ffff88801ebde2e0 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
ffff88801ebde2e0 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (slock-AF_PHONET){+...}-{3:3}:
rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56
spin_lock include/linux/spinlock_rt.h:45 [inline]
__sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_indicate net/phonet/pep.c:123 [inline]
pipe_snd_status+0x1f1/0x320 net/phonet/pep.c:221
pipe_grant_credits net/phonet/pep.c:244 [inline]
pipe_do_rcv+0xf15/0x16a0 net/phonet/pep.c:433
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__release_sock+0x2a9/0x3d0 net/core/sock.c:3216
release_sock+0x1be/0x290 net/core/sock.c:3815
pep_sock_accept+0xd47/0x11e0 net/phonet/pep.c:879
pn_socket_accept+0xc1/0x310 net/phonet/socket.c:303
do_accept+0x6ca/0x930 net/socket.c:2062
__sys_accept4_file net/socket.c:2096 [inline]
__sys_accept4+0x139/0x230 net/socket.c:2118
__do_sys_accept4 net/socket.c:2125 [inline]
__se_sys_accept4 net/socket.c:2122 [inline]
__x64_sys_accept4+0x9a/0xb0 net/socket.c:2122

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (slock-AF_PHONET/1){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3167 [inline]
check_prevs_add kernel/locking/lockdep.c:3286 [inline]
validate_chain kernel/locking/lockdep.c:3910 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64
__sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1
pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34
__sock_release+0xb9/0x250 net/socket.c:726
sock_close+0x1c/0x30 net/socket.c:1529
__fput+0x461/0xa70 fs/file_table.c:510
fput_close_sync+0x11f/0x240 fs/file_table.c:615
__do_sys_close fs/open.c:1507 [inline]
__se_sys_close fs/open.c:1492 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1492

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(slock-AF_PHONET);
lock(slock-AF_PHONET/1);
lock(slock-AF_PHONET);
lock(slock-AF_PHONET/1);

*** DEADLOCK ***

7 locks held by syz-executor220/8545:
#0: ffff88804d147578 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline]
#0: ffff88804d147578 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x89/0x250 net/socket.c:725
#1: ffff88801ebd8c18 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
#1: ffff88801ebd8c18 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: pep_sock_close+0x86/0x5b0 net/phonet/pep.c:742
#2: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x271/0xc60 net/core/dev.c:6673
#4: ffff88801ebde2e0 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#4: ffff88801ebde2e0 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
#6: ffff88801ebde398 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2022 [inline]
#6: ffff88801ebde398 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1

stack backtrace:
CPU: 1 UID: 0 PID: 8545 Comm: syz-executor220 Not tainted syzkaller #0 PREEMPT_{RT,(full)}

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026

Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3167 [inline]
check_prevs_add kernel/locking/lockdep.c:3286 [inline]
validate_chain kernel/locking/lockdep.c:3910 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64
__sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1
pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34
__sock_release+0xb9/0x250 net/socket.c:726
sock_close+0x1c/0x30 net/socket.c:1529
__fput+0x461/0xa70 fs/file_table.c:510
fput_close_sync+0x11f/0x240 fs/file_table.c:615
__do_sys_close fs/open.c:1507 [inline]
__se_sys_close fs/open.c:1492 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1492

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f1251e9b98e
Code: 08 0f 85 65 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007ffdde912fb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 0000555572330400 RCX: 00007f1251e9b98e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000007870a
R13: 000000000007873c R14: 00007f1251f36b7c R15: 00007f1251f36b60
</TASK>


Tested on:

commit: bee6ea30 Add linux-next specific files for 20260421
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=16d8a2d2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=354b135d724a721f
dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=11c45f16580000

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __sk_receive_skb

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------

syz-executor150/8596 is trying to acquire lock:
ffff888039b2c8a0 (slock-AF_PHONET/1){+.+.}-{3:3}, at: __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563

but task is already holding lock:

ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565

7 locks held by syz-executor150/8596:
#0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline]
#0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x89/0x250 net/socket.c:725
#1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
#1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: pep_sock_close+0x86/0x5b0 net/phonet/pep.c:742

#2: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x271/0xc60 net/core/dev.c:6673

#4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565

#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57

#6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2022 [inline]
#6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1

stack backtrace:
CPU: 0 UID: 0 PID: 8596 Comm: syz-executor150 Not tainted syzkaller #0 PREEMPT_{RT,(full)}

RIP: 0033:0x7fd3c4acf98e

Code: 08 0f 85 65 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08

RSP: 002b:00007ffcc0cf80b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00005555771d0400 RCX: 00007fd3c4acf98e

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000077f63
R13: 0000000000077f95 R14: 00007fd3c4b6ab6c R15: 00007fd3c4b6ab60

</TASK>


Tested on:

commit: bee6ea30 Add linux-next specific files for 20260421

git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=124bd702580000

kernel config: https://syzkaller.appspot.com/x/.config?x=354b135d724a721f
dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=17c45f16580000