------------[ cut here ]------------
WARNING: CPU: 0 PID: 8303 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: 8303 Comm: syz.1.1749 Not tainted 6.12.0-rc6-syzkaller #0
Hardware name: ARM-Versatile Express
Call trace: 
[<8199c7f8>] (dump_backtrace) from [<8199c8f4>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:00000000 r6:82622f44 r5:00000000 r4:8203db14
[<8199c8dc>] (show_stack) from [<819bad88>] (__dump_stack lib/dump_stack.c:94 [inline])
[<8199c8dc>] (show_stack) from [<819bad88>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:120)
[<819bad34>] (dump_stack_lvl) from [<819badc8>] (dump_stack+0x18/0x1c lib/dump_stack.c:129)
 r5:00000000 r4:82870d18
[<819badb0>] (dump_stack) from [<8199d420>] (panic+0x120/0x374 kernel/panic.c:354)
[<8199d300>] (panic) from [<80242118>] (check_panic_on_warn kernel/panic.c:243 [inline])
[<8199d300>] (panic) from [<80242118>] (get_taint+0x0/0x1c kernel/panic.c:238)
 r3:8260c5c4 r2:00000001 r1:82025ee8 r0:8202d950
 r7:80840670
[<802420a4>] (check_panic_on_warn) from [<8024227c>] (__warn+0x80/0x188 kernel/panic.c:748)
[<802421fc>] (__warn) from [<8024256c>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:783)
 r8:00000009 r7:8208c310 r6:eaca9c84 r5:8373e000 r4:00000000
[<80242388>] (warn_slowpath_fmt) from [<80840670>] (refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28)
 r10:00000000 r9:852bbe84 r8:00000000 r7:00000000 r6:81829ec4 r5:00000002
 r4:84f27600
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (__refcount_sub_and_test include/linux/refcount.h:275 [inline])
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (__refcount_dec_and_test include/linux/refcount.h:307 [inline])
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (refcount_dec_and_test include/linux/refcount.h:325 [inline])
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (skb_unref include/linux/skbuff.h:1232 [inline])
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (__sk_skb_reason_drop net/core/skbuff.c:1213 [inline])
[<80840534>] (refcount_warn_saturate) from [<8149b980>] (sk_skb_reason_drop+0x1d8/0x248 net/core/skbuff.c:1241)
[<8149b7a8>] (sk_skb_reason_drop) from [<81829ec4>] (kfree_skb_reason include/linux/skbuff.h:1262 [inline])
[<8149b7a8>] (sk_skb_reason_drop) from [<81829ec4>] (kfree_skb include/linux/skbuff.h:1271 [inline])
[<8149b7a8>] (sk_skb_reason_drop) from [<81829ec4>] (j1939_session_destroy+0x78/0x200 net/can/j1939/transport.c:282)
 r9:852bbe84 r8:00000000 r7:eaca9f38 r6:84757c50 r5:84757c00 r4:84f27600
[<81829e4c>] (j1939_session_destroy) from [<8182b1e0>] (__j1939_session_release net/can/j1939/transport.c:294 [inline])
[<81829e4c>] (j1939_session_destroy) from [<8182b1e0>] (kref_put include/linux/kref.h:65 [inline])
[<81829e4c>] (j1939_session_destroy) from [<8182b1e0>] (j1939_session_put+0x54/0x58 net/can/j1939/transport.c:299)
 r6:84757c00 r5:8328af00 r4:00000004
[<8182b18c>] (j1939_session_put) from [<81829210>] (j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline])
[<8182b18c>] (j1939_session_put) from [<81829210>] (j1939_sk_sendmsg+0x41c/0x548 net/can/j1939/socket.c:1277)
[<81828df4>] (j1939_sk_sendmsg) from [<81486614>] (sock_sendmsg_nosec net/socket.c:729 [inline])
[<81828df4>] (j1939_sk_sendmsg) from [<81486614>] (__sock_sendmsg+0x44/0x78 net/socket.c:744)
 r10:00000000 r9:eaca9dd4 r8:eaca9dd4 r7:8328af00 r6:8328af00 r5:eaca9f38
 r4:00000000
[<814865d0>] (__sock_sendmsg) from [<81487614>] (____sys_sendmsg+0x2a4/0x2c4 net/socket.c:2607)
 r7:8328af00 r6:00000000 r5:00000000 r4:eaca9f38
[<81487370>] (____sys_sendmsg) from [<8148957c>] (___sys_sendmsg+0x9c/0xd0 net/socket.c:2661)
 r10:eaca9e34 r9:20000180 r8:00000000 r7:00000000 r6:8328af00 r5:eaca9f38
 r4:00000000
[<814894e0>] (___sys_sendmsg) from [<81489a94>] (__sys_sendmsg net/socket.c:2690 [inline])
[<814894e0>] (___sys_sendmsg) from [<81489a94>] (__do_sys_sendmsg net/socket.c:2699 [inline])
[<814894e0>] (___sys_sendmsg) from [<81489a94>] (sys_sendmsg+0x78/0xbc net/socket.c:2697)
 r10:00000128 r9:8373e000 r8:8020029c r7:00000000 r6:20000180 r5:8328af00
 r4:00000000
[<81489a1c>] (sys_sendmsg) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xeaca9fa8 to 0xeaca9ff0)
9fa0:                   00000000 00000000 00000004 20000180 00000000 00000000
9fc0: 00000000 00000000 002862f0 00000128 00000000 00006364 003d0f00 76b8a0bc
9fe0: 76b89ec0 76b89eb0 00018b10 00133470
 r7:00000128 r6:002862f0 r5:00000000 r4:00000000
Rebooting in 86400 seconds..