bisecting fixing commit since 961f830af0658ef5ef8a7708786d634a6115f16b building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66 testing commit 961f830af0658ef5ef8a7708786d634a6115f16b with gcc (GCC) 8.4.1 20210217 kernel signature: cfdcc61c4e32385afa1c16a8710202489e49f39ed43229b3a382eb064dac07f8 run #0: crashed: KASAN: use-after-free Read in lock_sock_nested run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #2: crashed: KASAN: use-after-free Read in lock_sock_nested run #3: crashed: KASAN: use-after-free Read in lock_sock_nested run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #6: crashed: KASAN: use-after-free Read in lock_sock_nested run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #8: crashed: KASAN: use-after-free Read in lock_sock_nested run #9: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #10: crashed: KASAN: use-after-free Read in lock_sock_nested run #11: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #12: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #13: crashed: KASAN: use-after-free Read in lock_sock_nested run #14: crashed: KASAN: use-after-free Read in lock_sock_nested run #15: crashed: KASAN: use-after-free Read in lock_sock_nested run #16: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #17: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #18: crashed: KASAN: use-after-free Read in lock_sock_nested run #19: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put testing current HEAD 1e986fe9ad15b8406034c504afc5ae76f0a8e852 testing commit 1e986fe9ad15b8406034c504afc5ae76f0a8e852 with gcc (GCC) 8.4.1 20210217 kernel signature: e54b7b1d01bd3fb7c968554438ced516036c9fb8f3fec7f064846fbdb01fd8aa run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #2: crashed: KASAN: use-after-free Read in lock_sock_nested run #3: crashed: KASAN: use-after-free Read in lock_sock_nested run #4: crashed: KASAN: use-after-free Read in lock_sock_nested run #5: crashed: KASAN: use-after-free Read in lock_sock_nested run #6: crashed: KASAN: use-after-free Read in lock_sock_nested run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #9: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put revisions tested: 2, total time: 39m48.015447746s (build: 26m55.926748845s, test: 12m17.036260646s) the crash still happens on HEAD commit msg: Linux 4.19.191 crash: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP KASAN CPU: 0 PID: 2670 Comm: kworker/0:2 Not tainted 4.19.191-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events l2cap_chan_timeout RIP: 0010:refcount_dec_and_test arch/x86/include/asm/refcount.h:76 [inline] RIP: 0010:kref_put include/linux/kref.h:69 [inline] RIP: 0010:l2cap_chan_put+0xd/0x1a0 net/bluetooth/l2cap_core.c:498 Code: 8b 45 d0 e9 ef fe ff ff 48 89 df e8 5d ad 7a fb e9 9d fe ff ff 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 ff 4f 18 0f 88 8b e7 c4 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d RSP: 0018:ffff8881e8f3fcd0 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8881d46235c0 RCX: 1ffff1103d1d817c RDX: 1ffff1103a8c4748 RSI: ffff8881e8ec0bc0 RDI: 0000000000000000 RBP: ffff8881e8f3fcf8 R08: ffff8881e8ec0be0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d4622d40 R13: ffff8881e03b7438 R14: ffff8881d46231a8 R15: ffff8881d4622e50 FS: 0000000000000000(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 000000000846d006 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: l2cap_sock_kill.part.2+0x32/0x60 net/bluetooth/l2cap_sock.c:1061 l2cap_sock_kill net/bluetooth/l2cap_sock.c:1332 [inline] l2cap_sock_close_cb+0x84/0xa0 net/bluetooth/l2cap_sock.c:1331 l2cap_chan_timeout+0x163/0x1c0 net/bluetooth/l2cap_core.c:432 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2152 worker_thread+0x85/0xb60 kernel/workqueue.c:2295 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Modules linked in: CR2: 0000000000000018 ---[ end trace d8c5b41332d48516 ]--- RIP: 0010:refcount_dec_and_test arch/x86/include/asm/refcount.h:76 [inline] RIP: 0010:kref_put include/linux/kref.h:69 [inline] RIP: 0010:l2cap_chan_put+0xd/0x1a0 net/bluetooth/l2cap_core.c:498 Code: 8b 45 d0 e9 ef fe ff ff 48 89 df e8 5d ad 7a fb e9 9d fe ff ff 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 ff 4f 18 0f 88 8b e7 c4 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d RSP: 0018:ffff8881e8f3fcd0 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8881d46235c0 RCX: 1ffff1103d1d817c RDX: 1ffff1103a8c4748 RSI: ffff8881e8ec0bc0 RDI: 0000000000000000 RBP: ffff8881e8f3fcf8 R08: ffff8881e8ec0be0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d4622d40 R13: ffff8881e03b7438 R14: ffff8881d46231a8 R15: ffff8881d4622e50 FS: 0000000000000000(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 000000000846d006 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400