bisecting fixing commit since 961f830af0658ef5ef8a7708786d634a6115f16b building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66 testing commit 961f830af0658ef5ef8a7708786d634a6115f16b with gcc (GCC) 8.1.0 kernel signature: 1c7621e32b45077137cb9788bf7e3b16b85b779d04b29cfdd301f21cb7a4c961 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: 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: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put 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 a1b977b49b66c75e6c51a515f6700371ae720217 testing commit a1b977b49b66c75e6c51a515f6700371ae720217 with gcc (GCC) 8.1.0 kernel signature: 25d090e3736de4e67860ab8c4f5044be4c3e494a5917020eaf910f0dc00c70f0 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: 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: 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: 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: 31m12.896349317s (build: 18m56.426054958s, test: 11m21.530647137s) the crash still happens on HEAD commit msg: Linux 4.19.150 crash: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 PGD 93409067 P4D 93409067 PUD 9340d067 PMD 0 Oops: 0002 [#1] PREEMPT SMP KASAN CPU: 1 PID: 3398 Comm: kworker/1:2 Not tainted 4.19.150-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 3d a7 69 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 b9 8a ae 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d RSP: 0018:ffff88809b26fcd0 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8880a44ca5c0 RCX: 1ffff1101364816c RDX: 1ffff11014899548 RSI: ffff88809b240b40 RDI: 0000000000000000 RBP: ffff88809b26fcf8 R08: ffff88809b240b60 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880746cb100 R13: ffff8880a987bd38 R14: ffff8880746cb568 R15: ffff8880746cb210 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 00000000a518c000 CR4: 00000000001406e0 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 de27e18ef682fdc1 ]--- 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 3d a7 69 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 b9 8a ae 00 74 0b 5b 41 5c 41 5d 41 5e 41 5f 5d RSP: 0018:ffff88809b26fcd0 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8880a44ca5c0 RCX: 1ffff1101364816c RDX: 1ffff11014899548 RSI: ffff88809b240b40 RDI: 0000000000000000 RBP: ffff88809b26fcf8 R08: ffff88809b240b60 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880746cb100 R13: ffff8880a987bd38 R14: ffff8880746cb568 R15: ffff8880746cb210 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 00000000a518c000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400