------------[ cut here ]------------
WARNING: CPU: 0 PID: 17742 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: 17742 Comm: syz.1.5319 Not tainted 6.11.0-syzkaller #0
Hardware name: ARM-Versatile Express
Call trace: 
[<8198c4e0>] (dump_backtrace) from [<8198c5dc>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:00000000 r6:826228c4 r5:00000000 r4:820390a8
[<8198c5c4>] (show_stack) from [<819aa8c4>] (__dump_stack lib/dump_stack.c:93 [inline])
[<8198c5c4>] (show_stack) from [<819aa8c4>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:119)
[<819aa870>] (dump_stack_lvl) from [<819aa904>] (dump_stack+0x18/0x1c lib/dump_stack.c:128)
 r5:00000000 r4:82870d18
[<819aa8ec>] (dump_stack) from [<8198d108>] (panic+0x120/0x374 kernel/panic.c:354)
[<8198cfe8>] (panic) from [<802421dc>] (check_panic_on_warn kernel/panic.c:243 [inline])
[<8198cfe8>] (panic) from [<802421dc>] (get_taint+0x0/0x1c kernel/panic.c:238)
 r3:8260c5c4 r2:00000001 r1:820210f0 r0:82028eb4
 r7:80839f38
[<80242168>] (check_panic_on_warn) from [<80242340>] (__warn+0x80/0x188 kernel/panic.c:748)
[<802422c0>] (__warn) from [<80242630>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:783)
 r8:00000009 r7:82087dc4 r6:dff9dc84 r5:83646000 r4:00000000
[<8024244c>] (warn_slowpath_fmt) from [<80839f38>] (refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28)
 r10:00000000 r9:85710684 r8:00000000 r7:00000000 r6:8181a4d4 r5:00000002
 r4:857db540
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (__refcount_sub_and_test include/linux/refcount.h:275 [inline])
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (__refcount_dec_and_test include/linux/refcount.h:307 [inline])
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (refcount_dec_and_test include/linux/refcount.h:325 [inline])
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (skb_unref include/linux/skbuff.h:1232 [inline])
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (__sk_skb_reason_drop net/core/skbuff.c:1213 [inline])
[<80839dfc>] (refcount_warn_saturate) from [<8148cd70>] (sk_skb_reason_drop+0x1d8/0x248 net/core/skbuff.c:1241)
[<8148cb98>] (sk_skb_reason_drop) from [<8181a4d4>] (kfree_skb_reason include/linux/skbuff.h:1262 [inline])
[<8148cb98>] (sk_skb_reason_drop) from [<8181a4d4>] (kfree_skb include/linux/skbuff.h:1271 [inline])
[<8148cb98>] (sk_skb_reason_drop) from [<8181a4d4>] (j1939_session_destroy+0x78/0x200 net/can/j1939/transport.c:282)
 r9:85710684 r8:00000000 r7:dff9df38 r6:85002850 r5:85002800 r4:857db540
[<8181a45c>] (j1939_session_destroy) from [<8181b7f0>] (__j1939_session_release net/can/j1939/transport.c:294 [inline])
[<8181a45c>] (j1939_session_destroy) from [<8181b7f0>] (kref_put include/linux/kref.h:65 [inline])
[<8181a45c>] (j1939_session_destroy) from [<8181b7f0>] (j1939_session_put+0x54/0x58 net/can/j1939/transport.c:299)
 r6:85002800 r5:84c0fb80 r4:00000004
[<8181b79c>] (j1939_session_put) from [<81819824>] (j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline])
[<8181b79c>] (j1939_session_put) from [<81819824>] (j1939_sk_sendmsg+0x41c/0x548 net/can/j1939/socket.c:1277)
[<81819408>] (j1939_sk_sendmsg) from [<81477a1c>] (sock_sendmsg_nosec net/socket.c:730 [inline])
[<81819408>] (j1939_sk_sendmsg) from [<81477a1c>] (__sock_sendmsg+0x44/0x78 net/socket.c:745)
 r10:00000000 r9:dff9ddd4 r8:dff9ddd4 r7:00000000 r6:84c0fb80 r5:dff9df38
 r4:00000000
[<814779d8>] (__sock_sendmsg) from [<81478a20>] (____sys_sendmsg+0x2ac/0x2cc net/socket.c:2603)
 r7:00000000 r6:00000000 r5:84c0fb80 r4:dff9df38
[<81478774>] (____sys_sendmsg) from [<8147a98c>] (___sys_sendmsg+0x9c/0xd0 net/socket.c:2657)
 r10:dff9de34 r9:20000180 r8:00000000 r7:00000000 r6:84c0fb80 r5:dff9df38
 r4:00000000
[<8147a8f0>] (___sys_sendmsg) from [<8147aea4>] (__sys_sendmsg net/socket.c:2686 [inline])
[<8147a8f0>] (___sys_sendmsg) from [<8147aea4>] (__do_sys_sendmsg net/socket.c:2695 [inline])
[<8147a8f0>] (___sys_sendmsg) from [<8147aea4>] (sys_sendmsg+0x78/0xbc net/socket.c:2693)
 r10:00000128 r9:83646000 r8:8020029c r7:00000000 r6:20000180 r5:84c0fb80
 r4:00000000
[<8147ae2c>] (sys_sendmsg) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xdff9dfa8 to 0xdff9dff0)
dfa0:                   00000000 00000000 00000004 20000180 00000000 00000000
dfc0: 00000000 00000000 002862f0 00000128 00000000 00006364 003d0f00 76b530bc
dfe0: 76b52ec0 76b52eb0 000189e8 00132db0
 r7:00000128 r6:002862f0 r5:00000000 r4:00000000
Rebooting in 86400 seconds..