bisecting fixing commit since 961f830af0658ef5ef8a7708786d634a6115f16b
building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66
testing commit 961f830af0658ef5ef8a7708786d634a6115f16b with gcc (GCC) 8.1.0
kernel signature: fa690aa2657c86aa9bbf0f319c37fa4e204093551e64e423c0c6813fc5d7d27d
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: KASAN: use-after-free Read in lock_sock_nested
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: KASAN: use-after-free Read in lock_sock_nested
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: KASAN: use-after-free Read in lock_sock_nested
run #8: crashed: KASAN: use-after-free Read in lock_sock_nested
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing current HEAD 3207316b3beec7e38e5dbe2f463df0cec71e0b97
testing commit 3207316b3beec7e38e5dbe2f463df0cec71e0b97 with gcc (GCC) 8.1.0
kernel signature: 29d0c08a71effffe48c28f6a7dbbdc2993346fb3226ac17f9e179e21a5bc8e05
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: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
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: KASAN: use-after-free Read in lock_sock_nested
run #6: crashed: KASAN: use-after-free Read in lock_sock_nested
run #7: crashed: KASAN: use-after-free Read in lock_sock_nested
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: 28m33.128441858s (build: 18m3.319079276s, test: 9m57.49969237s)
the crash still happens on HEAD
commit msg: Linux 4.19.164
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: 1 PID: 19 Comm: kworker/1:0 Not tainted 4.19.164-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:496
Code: 8b 45 d0 e9 ef fe ff ff 48 89 df e8 0d ce 68 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 <f0> ff 4f 18 0f 88 bb 8a ae 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d
RSP: 0018:ffff8881f5757cd0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8881e59b0d40 RCX: 1ffff1103eae91c4
RDX: 1ffff1103cb36238 RSI: ffff8881f5748e00 RDI: 0000000000000000
RBP: ffff8881f5757cf8 R08: ffff8881f5748e20 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d3ebf2c0
R13: ffff8881d810eb38 R14: ffff8881d3ebf728 R15: ffff8881d3ebf3d0
FS:  0000000000000000(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000018 CR3: 000000000846d006 CR4: 00000000001606e0
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:1053
 l2cap_sock_kill net/bluetooth/l2cap_sock.c:1324 [inline]
 l2cap_sock_close_cb+0x84/0xa0 net/bluetooth/l2cap_sock.c:1323
 l2cap_chan_timeout+0x163/0x1c0 net/bluetooth/l2cap_core.c:432
 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2155
 worker_thread+0x85/0xb60 kernel/workqueue.c:2298
 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 13b6e23c571cc389 ]---
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:496
Code: 8b 45 d0 e9 ef fe ff ff 48 89 df e8 0d ce 68 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 <f0> ff 4f 18 0f 88 bb 8a ae 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d
RSP: 0018:ffff8881f5757cd0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8881e59b0d40 RCX: 1ffff1103eae91c4
RDX: 1ffff1103cb36238 RSI: ffff8881f5748e00 RDI: 0000000000000000
RBP: ffff8881f5757cf8 R08: ffff8881f5748e20 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d3ebf2c0
R13: ffff8881d810eb38 R14: ffff8881d3ebf728 R15: ffff8881d3ebf3d0
FS:  0000000000000000(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000018 CR3: 000000000846d006 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400