bisecting fixing commit since ab9dfda232481dcfaf549ce774004d116fc80c13 building syzkaller on 37bccd4ed9e71025cd84e857f9ffca4ec8451c6b testing commit ab9dfda232481dcfaf549ce774004d116fc80c13 with gcc (GCC) 8.1.0 kernel signature: cffa4bd4f55f501a684f9dd87d120e0a34af05ea873275ed7df8773f71a7f9d5 run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close testing current HEAD b850307b279cbd12ab8c654d1a3dfe55319cc475 testing commit b850307b279cbd12ab8c654d1a3dfe55319cc475 with gcc (GCC) 8.1.0 kernel signature: 60db5fd0f1babb44227ac6ee2f8c0a1d67450c7cb1fc39565b4510f68ef754a3 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 Read in l2cap_chan_close run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: OK run #7: OK run #8: OK run #9: basic kernel testing failed: failed to copy test binary to VM: timedout ["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-executor799674839" "root@10.128.15.206:./syz-executor799674839"] Warning: Permanently added '10.128.15.206' (ECDSA) to the list of known hosts. revisions tested: 2, total time: 31m50.255684542s (build: 17m7.055984218s, test: 13m42.342606588s) the crash still happens on HEAD commit msg: Linux 4.14.184 crash: KASAN: use-after-free Read in l2cap_chan_close IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready ================================================================== BUG: KASAN: use-after-free in l2cap_chan_close+0x4fd/0x7e0 net/bluetooth/l2cap_core.c:727 Read of size 1 at addr ffff88808790d5a0 by task kworker/0:2/3329 CPU: 0 PID: 3329 Comm: kworker/0:2 Not tainted 4.14.184-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 18: 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 18: 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 ffff88808790d580 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff88808790d580, ffff88808790dd80) The buggy address belongs to the page: page:ffffea00021e4300 count:1 mapcount:0 mapping:ffff88808790c480 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff88808790c480 0000000000000000 0000000100000003 raw: ffffea000221fd20 ffffea00021e22a0 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88808790d480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808790d500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88808790d580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88808790d600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808790d680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================