------------[ cut here ]------------
WARNING: CPU: 1 PID: 9340 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: 1 UID: 0 PID: 9340 Comm: syz.5.1000 Not tainted 6.12.0-rc7-syzkaller #0
Hardware name: ARM-Versatile Express
Call trace: 
[<8199d478>] (dump_backtrace) from [<8199d574>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:00000000 r6:82622f44 r5:00000000 r4:8203df50
[<8199d55c>] (show_stack) from [<819bba40>] (__dump_stack lib/dump_stack.c:94 [inline])
[<8199d55c>] (show_stack) from [<819bba40>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:120)
[<819bb9ec>] (dump_stack_lvl) from [<819bba80>] (dump_stack+0x18/0x1c lib/dump_stack.c:129)
 r5:00000000 r4:82870d18
[<819bba68>] (dump_stack) from [<8199e0a0>] (panic+0x120/0x374 kernel/panic.c:354)
[<8199df80>] (panic) from [<802420d8>] (check_panic_on_warn kernel/panic.c:243 [inline])
[<8199df80>] (panic) from [<802420d8>] (get_taint+0x0/0x1c kernel/panic.c:238)
 r3:8260c5c4 r2:00000001 r1:82026324 r0:8202dd8c
 r7:80840e00
[<80242064>] (check_panic_on_warn) from [<8024223c>] (__warn+0x80/0x188 kernel/panic.c:748)
[<802421bc>] (__warn) from [<8024252c>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:783)
 r8:00000009 r7:8208c778 r6:e0005c84 r5:84368c00 r4:00000000
[<80242348>] (warn_slowpath_fmt) from [<80840e00>] (refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28)
 r10:00000000 r9:85680284 r8:00000000 r7:00000000 r6:8182aacc r5:00000002
 r4:8534dcc0
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (__refcount_sub_and_test include/linux/refcount.h:275 [inline])
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (__refcount_dec_and_test include/linux/refcount.h:307 [inline])
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (refcount_dec_and_test include/linux/refcount.h:325 [inline])
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (skb_unref include/linux/skbuff.h:1232 [inline])
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (__sk_skb_reason_drop net/core/skbuff.c:1213 [inline])
[<80840cc4>] (refcount_warn_saturate) from [<8149c5a8>] (sk_skb_reason_drop+0x1d8/0x248 net/core/skbuff.c:1241)
[<8149c3d0>] (sk_skb_reason_drop) from [<8182aacc>] (kfree_skb_reason include/linux/skbuff.h:1262 [inline])
[<8149c3d0>] (sk_skb_reason_drop) from [<8182aacc>] (kfree_skb include/linux/skbuff.h:1271 [inline])
[<8149c3d0>] (sk_skb_reason_drop) from [<8182aacc>] (j1939_session_destroy+0x78/0x200 net/can/j1939/transport.c:282)
 r9:85680284 r8:00000000 r7:e0005f38 r6:8502a450 r5:8502a400 r4:8534dcc0
[<8182aa54>] (j1939_session_destroy) from [<8182bde8>] (__j1939_session_release net/can/j1939/transport.c:294 [inline])
[<8182aa54>] (j1939_session_destroy) from [<8182bde8>] (kref_put include/linux/kref.h:65 [inline])
[<8182aa54>] (j1939_session_destroy) from [<8182bde8>] (j1939_session_put+0x54/0x58 net/can/j1939/transport.c:299)
 r6:8502a400 r5:84418a00 r4:00000002
[<8182bd94>] (j1939_session_put) from [<81829e18>] (j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline])
[<8182bd94>] (j1939_session_put) from [<81829e18>] (j1939_sk_sendmsg+0x41c/0x548 net/can/j1939/socket.c:1277)
[<818299fc>] (j1939_sk_sendmsg) from [<81487204>] (sock_sendmsg_nosec net/socket.c:729 [inline])
[<818299fc>] (j1939_sk_sendmsg) from [<81487204>] (__sock_sendmsg+0x44/0x78 net/socket.c:744)
 r10:00000000 r9:e0005dd4 r8:e0005dd4 r7:84418a00 r6:84418a00 r5:e0005f38
 r4:00000000
[<814871c0>] (__sock_sendmsg) from [<81488204>] (____sys_sendmsg+0x2a4/0x2c4 net/socket.c:2607)
 r7:84418a00 r6:00000000 r5:00000001 r4:e0005f38
[<81487f60>] (____sys_sendmsg) from [<8148a16c>] (___sys_sendmsg+0x9c/0xd0 net/socket.c:2661)
 r10:e0005e34 r9:20001200 r8:00000001 r7:00000000 r6:84418a00 r5:e0005f38
 r4:00000000
[<8148a0d0>] (___sys_sendmsg) from [<8148a684>] (__sys_sendmsg net/socket.c:2690 [inline])
[<8148a0d0>] (___sys_sendmsg) from [<8148a684>] (__do_sys_sendmsg net/socket.c:2699 [inline])
[<8148a0d0>] (___sys_sendmsg) from [<8148a684>] (sys_sendmsg+0x78/0xbc net/socket.c:2697)
 r10:00000128 r9:84368c00 r8:8020029c r7:00000001 r6:20001200 r5:84418a00
 r4:00000000
[<8148a60c>] (sys_sendmsg) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xe0005fa8 to 0xe0005ff0)
5fa0:                   00000000 00000000 00000003 20001200 00000001 00000000
5fc0: 00000000 00000000 002862f0 00000128 00000000 00006364 003d0f00 76b7e0bc
5fe0: 76b7dec0 76b7deb0 00018af0 00133450
 r7:00000128 r6:002862f0 r5:00000000 r4:00000000
Rebooting in 86400 seconds..