------------[ cut here ]------------
WARNING: CPU: 1 PID: 6698 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: 6698 Comm: syz.0.1320 Not tainted 6.11.0-syzkaller #0
Hardware name: ARM-Versatile Express
Call trace: 
[<81966cb8>] (dump_backtrace) from [<81966db4>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
 r7:00000000 r6:826228c4 r5:00000000 r4:8200e404
[<81966d9c>] (show_stack) from [<81984a58>] (__dump_stack lib/dump_stack.c:93 [inline])
[<81966d9c>] (show_stack) from [<81984a58>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:119)
[<81984a04>] (dump_stack_lvl) from [<81984a98>] (dump_stack+0x18/0x1c lib/dump_stack.c:128)
 r5:00000000 r4:8286ed18
[<81984a80>] (dump_stack) from [<8196785c>] (panic+0x120/0x368 kernel/panic.c:354)
[<8196773c>] (panic) from [<802421d4>] (check_panic_on_warn kernel/panic.c:243 [inline])
[<8196773c>] (panic) from [<802421d4>] (get_taint+0x0/0x1c kernel/panic.c:238)
 r3:8260c5c4 r2:00000001 r1:81ff6c38 r0:81ffea04
 r7:8081a110
[<80242160>] (check_panic_on_warn) from [<80242328>] (__warn+0x7c/0x180 kernel/panic.c:741)
[<802422ac>] (__warn) from [<80242614>] (warn_slowpath_fmt+0x1e8/0x1f4 kernel/panic.c:774)
 r8:00000009 r7:8205cdc4 r6:df885c84 r5:8410a400 r4:00000000
[<80242430>] (warn_slowpath_fmt) from [<8081a110>] (refcount_warn_saturate+0x13c/0x174 lib/refcount.c:28)
 r10:00000000 r9:84d8a284 r8:00000000 r7:00000000 r6:817f4e34 r5:00000002
 r4:8583c600
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (__refcount_sub_and_test include/linux/refcount.h:275 [inline])
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (__refcount_dec_and_test include/linux/refcount.h:307 [inline])
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (refcount_dec_and_test include/linux/refcount.h:325 [inline])
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (skb_unref include/linux/skbuff.h:1232 [inline])
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (__sk_skb_reason_drop net/core/skbuff.c:1213 [inline])
[<80819fd4>] (refcount_warn_saturate) from [<8146782c>] (sk_skb_reason_drop+0x1d8/0x248 net/core/skbuff.c:1241)
[<81467654>] (sk_skb_reason_drop) from [<817f4e34>] (kfree_skb_reason include/linux/skbuff.h:1262 [inline])
[<81467654>] (sk_skb_reason_drop) from [<817f4e34>] (kfree_skb include/linux/skbuff.h:1271 [inline])
[<81467654>] (sk_skb_reason_drop) from [<817f4e34>] (j1939_session_destroy+0x78/0x200 net/can/j1939/transport.c:282)
 r9:84d8a284 r8:00000000 r7:df885f38 r6:8506bc50 r5:8506bc00 r4:8583c600
[<817f4dbc>] (j1939_session_destroy) from [<817f6150>] (__j1939_session_release net/can/j1939/transport.c:294 [inline])
[<817f4dbc>] (j1939_session_destroy) from [<817f6150>] (kref_put include/linux/kref.h:65 [inline])
[<817f4dbc>] (j1939_session_destroy) from [<817f6150>] (j1939_session_put+0x54/0x58 net/can/j1939/transport.c:299)
 r6:8506bc00 r5:8490d680 r4:00000004
[<817f60fc>] (j1939_session_put) from [<817f4184>] (j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline])
[<817f60fc>] (j1939_session_put) from [<817f4184>] (j1939_sk_sendmsg+0x41c/0x548 net/can/j1939/socket.c:1277)
[<817f3d68>] (j1939_sk_sendmsg) from [<8145253c>] (sock_sendmsg_nosec net/socket.c:730 [inline])
[<817f3d68>] (j1939_sk_sendmsg) from [<8145253c>] (__sock_sendmsg+0x44/0x78 net/socket.c:745)
 r10:00000000 r9:df885dd4 r8:df885dd4 r7:00000000 r6:8490d680 r5:df885f38
 r4:00000000
[<814524f8>] (__sock_sendmsg) from [<81453540>] (____sys_sendmsg+0x2ac/0x2cc net/socket.c:2603)
 r7:00000000 r6:00000000 r5:8490d680 r4:df885f38
[<81453294>] (____sys_sendmsg) from [<814554ac>] (___sys_sendmsg+0x9c/0xd0 net/socket.c:2657)
 r10:df885e34 r9:20000180 r8:00000000 r7:00000000 r6:8490d680 r5:df885f38
 r4:00000000
[<81455410>] (___sys_sendmsg) from [<814559c4>] (__sys_sendmsg net/socket.c:2686 [inline])
[<81455410>] (___sys_sendmsg) from [<814559c4>] (__do_sys_sendmsg net/socket.c:2695 [inline])
[<81455410>] (___sys_sendmsg) from [<814559c4>] (sys_sendmsg+0x78/0xbc net/socket.c:2693)
 r10:00000128 r9:8410a400 r8:8020029c r7:00000000 r6:20000180 r5:8490d680
 r4:00000000
[<8145594c>] (sys_sendmsg) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xdf885fa8 to 0xdf885ff0)
5fa0:                   00000000 00000000 00000004 20000180 00000000 00000000
5fc0: 00000000 00000000 002862f0 00000128 00000000 00006364 003d0f00 76b510bc
5fe0: 76b50ec0 76b50eb0 000189d0 00132da0
 r7:00000128 r6:002862f0 r5:00000000 r4:00000000
Rebooting in 86400 seconds..