bisecting fixing commit since e0f8b8a65a473a8baa439cf865a694bbeb83fe90 building syzkaller on 06150bf1b39b70e521560bc943ac19b281903ebc testing commit e0f8b8a65a473a8baa439cf865a694bbeb83fe90 with gcc (GCC) 8.1.0 kernel signature: f75ceda44e5780c3f7233cef2882c1aa4ef5543463667f8578cb69f74164ad1e run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount run #5: crashed: KASAN: use-after-free Write in ex_handler_refcount run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close run #9: OK testing current HEAD 4520f06b03ae667e442da1ab9351fd28cd7ac598 testing commit 4520f06b03ae667e442da1ab9351fd28cd7ac598 with gcc (GCC) 8.1.0 kernel signature: 9b3e41ef803099b250bd3dbc56d6a6a174d2a72ccec52fb5bd3f7cb7ebee460f run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close run #8: basic kernel testing failed: failed to copy test binary to VM: failed to run ["scp" "-P" "22" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "BatchMode=yes" "-o" "IdentitiesOnly=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "-i" "/syzkaller/jobs/linux/workdir/image/key" "/tmp/syz-executor696588312" "root@10.128.0.12:./syz-executor696588312"]: exit status 1 Connection timed out during banner exchange lost connection run #9: OK revisions tested: 2, total time: 37m23.82690224s (build: 16m47.467428477s, test: 19m56.222825802s) the crash still happens on HEAD commit msg: Linux 4.14.175 crash: KASAN: use-after-free Read in l2cap_chan_close IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready NOHZ: local_softirq_pending 08 Bluetooth: psm cannot be added err -98 ================================================================== BUG: KASAN: use-after-free in l2cap_chan_close+0x4fd/0x7e0 net/bluetooth/l2cap_core.c:727 Read of size 1 at addr ffff888094c416a0 by task kworker/0:4/7077 CPU: 0 PID: 7077 Comm: kworker/0:4 Not tainted 4.14.175-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events do_enable_set Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427 l2cap_chan_close+0x4fd/0x7e0 net/bluetooth/l2cap_core.c:727 do_enable_set+0x45c/0x870 net/bluetooth/6lowpan.c:1086 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Allocated by task 7077: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x152/0x7a0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] l2cap_chan_create+0x41/0x380 net/bluetooth/l2cap_core.c:441 chan_create+0xa/0xc0 net/bluetooth/6lowpan.c:652 bt_6lowpan_listen net/bluetooth/6lowpan.c:971 [inline] do_enable_set+0x48f/0x870 net/bluetooth/6lowpan.c:1090 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Freed by task 23: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 l2cap_chan_destroy+0x132/0x1a0 net/bluetooth/l2cap_core.c:479 kref_put include/linux/kref.h:70 [inline] l2cap_chan_put+0x1e/0x20 net/bluetooth/l2cap_core.c:493 do_enable_set+0x468/0x870 net/bluetooth/6lowpan.c:1087 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 The buggy address belongs to the object at ffff888094c41680 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff888094c41680, ffff888094c41e80) The buggy address belongs to the page: page:ffffea0002531000 count:1 mapcount:0 mapping:ffff888094c40580 index:0xffff888094c40e00 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff888094c40580 ffff888094c40e00 0000000100000001 raw: ffff8880aa801938 ffffea00025230a0 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888094c41580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888094c41600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888094c41680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888094c41700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888094c41780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================