------------[ cut here ]------------
WARNING: CPU: 0 PID: 5896 at lib/refcount.c:28 refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28
refcount_t: underflow; use-after-free.
Modules linked in:
Kernel panic - not syncing: kernel: panic_on_warn set ...
CPU: 0 UID: 0 PID: 5896 Comm: syz.0.566 Not tainted 6.12.0-syzkaller #0
Hardware name: ARM-Versatile Express
Call trace: 
[<819be5f8>] (dump_backtrace) from [<819be6f4>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:00000000 r6:82623304 r5:00000000 r4:82043260
[<819be6dc>] (show_stack) from [<819dc71c>] (__dump_stack lib/dump_stack.c:94 [inline])
[<819be6dc>] (show_stack) from [<819dc71c>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:120)
[<819dc6c8>] (dump_stack_lvl) from [<819dc75c>] (dump_stack+0x18/0x1c lib/dump_stack.c:129)
 r5:00000000 r4:82871d18
[<819dc744>] (dump_stack) from [<819bf220>] (panic+0x120/0x374 kernel/panic.c:354)
[<819bf100>] (panic) from [<802426d0>] (check_panic_on_warn kernel/panic.c:243 [inline])
[<819bf100>] (panic) from [<802426d0>] (get_taint+0x0/0x1c kernel/panic.c:238)
 r3:8260c604 r2:00000001 r1:8202b7cc r0:82033298
 r7:80849f88
[<8024265c>] (check_panic_on_warn) from [<80242834>] (__warn+0x80/0x188 kernel/panic.c:748)
[<802427b4>] (__warn) from [<80242b24>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:783)
 r8:00000009 r7:82091f80 r6:ea9b9c74 r5:82efbc00 r4:00000000
[<80242940>] (warn_slowpath_fmt) from [<80849f88>] (refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28)
 r10:00000000 r9:84befe84 r8:00000000 r7:00000000 r6:8184859c r5:00000002
 r4:8414a3c0
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (__refcount_sub_and_test include/linux/refcount.h:275 [inline])
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (__refcount_dec_and_test include/linux/refcount.h:307 [inline])
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (refcount_dec_and_test include/linux/refcount.h:325 [inline])
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (skb_unref include/linux/skbuff.h:1233 [inline])
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (__sk_skb_reason_drop net/core/skbuff.c:1213 [inline])
[<80849e4c>] (refcount_warn_saturate) from [<814b0fac>] (sk_skb_reason_drop+0x1d8/0x248 net/core/skbuff.c:1241)
[<814b0dd4>] (sk_skb_reason_drop) from [<8184859c>] (kfree_skb_reason include/linux/skbuff.h:1263 [inline])
[<814b0dd4>] (sk_skb_reason_drop) from [<8184859c>] (kfree_skb include/linux/skbuff.h:1272 [inline])
[<814b0dd4>] (sk_skb_reason_drop) from [<8184859c>] (j1939_session_destroy+0x78/0x200 net/can/j1939/transport.c:282)
 r9:84befe84 r8:00000000 r7:ea9b9f20 r6:8487ba50 r5:8487ba00 r4:8414a3c0
[<81848524>] (j1939_session_destroy) from [<818498b8>] (__j1939_session_release net/can/j1939/transport.c:294 [inline])
[<81848524>] (j1939_session_destroy) from [<818498b8>] (kref_put include/linux/kref.h:65 [inline])
[<81848524>] (j1939_session_destroy) from [<818498b8>] (j1939_session_put+0x54/0x58 net/can/j1939/transport.c:299)
 r6:8487ba00 r5:84c3c780 r4:00000004
[<81849864>] (j1939_session_put) from [<818478e8>] (j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline])
[<81849864>] (j1939_session_put) from [<818478e8>] (j1939_sk_sendmsg+0x41c/0x548 net/can/j1939/socket.c:1277)
[<818474cc>] (j1939_sk_sendmsg) from [<8149bc48>] (sock_sendmsg_nosec net/socket.c:711 [inline])
[<818474cc>] (j1939_sk_sendmsg) from [<8149bc48>] (__sock_sendmsg+0x44/0x78 net/socket.c:726)
 r10:00000000 r9:ea9b9dc4 r8:ea9b9dc4 r7:84c3c780 r6:84c3c780 r5:ea9b9f20
 r4:00000000
[<8149bc04>] (__sock_sendmsg) from [<8149cc48>] (____sys_sendmsg+0x2a4/0x2c4 net/socket.c:2583)
 r7:84c3c780 r6:00000000 r5:00000000 r4:ea9b9f20
[<8149c9a4>] (____sys_sendmsg) from [<8149e9e0>] (___sys_sendmsg+0x9c/0xd0 net/socket.c:2637)
 r10:ea9b9e24 r9:20000280 r8:00000000 r7:00000000 r6:84c3c780 r5:ea9b9f20
 r4:00000000
[<8149e944>] (___sys_sendmsg) from [<8149ee70>] (__sys_sendmsg+0x8c/0xd8 net/socket.c:2669)
 r10:00000128 r9:82efbc00 r8:84ba06c0 r7:00000000 r6:20000280 r5:84ba06c1
 r4:00000006
[<8149ede4>] (__sys_sendmsg) from [<8149eed0>] (__do_sys_sendmsg net/socket.c:2674 [inline])
[<8149ede4>] (__sys_sendmsg) from [<8149eed0>] (sys_sendmsg+0x14/0x18 net/socket.c:2672)
 r8:8020029c r7:00000128 r6:002862f0 r5:00000000 r4:00000000
[<8149eebc>] (sys_sendmsg) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xea9b9fa8 to 0xea9b9ff0)
9fa0:                   00000000 00000000 00000006 20000280 00000000 00000000
9fc0: 00000000 00000000 002862f0 00000128 00000000 00006364 003d0f00 76bf10bc
9fe0: 76bf0ec0 76bf0eb0 00018af0 00133450
Rebooting in 86400 seconds..