bisecting fixing commit since b499cf4b3a901e87e1f933df04abf69b54de4457 building syzkaller on 5be3a391ba78f7f11b725cee6783880974b9895a testing commit b499cf4b3a901e87e1f933df04abf69b54de4457 with gcc (GCC) 8.1.0 kernel signature: e790cc81c132bf9fac41d5a98b9be87cd2a1179af804ff0132358527fd08eccb 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 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 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 Write in ex_handler_refcount testing current HEAD dda0e2920330128e0dbdeb11c8f25031aa40b11c testing commit dda0e2920330128e0dbdeb11c8f25031aa40b11c with gcc (GCC) 8.1.0 kernel signature: 906c94e30c5d4fc12bbebbf4023467a6f5134817873cdbe939ccf4d6d0819ff9 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 Write in ex_handler_refcount run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount 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 revisions tested: 2, total time: 25m31.967596346s (build: 17m38.140655433s, test: 7m12.787016634s) the crash still happens on HEAD commit msg: Linux 4.19.114 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 Bluetooth: psm cannot be added err -98 Bluetooth: psm cannot be added err -98 ================================================================== BUG: KASAN: use-after-free in l2cap_chan_close+0x536/0x830 net/bluetooth/l2cap_core.c:727 Read of size 1 at addr ffff88809e502360 by task kworker/1:3/7716 CPU: 1 PID: 7716 Comm: kworker/1:3 Not tainted 4.19.114-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:77 [inline] dump_stack+0x123/0x177 lib/dump_stack.c:118 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 l2cap_chan_close+0x536/0x830 net/bluetooth/l2cap_core.c:727 do_enable_set+0x47e/0x8b0 net/bluetooth/6lowpan.c:1086 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Allocated by task 7716: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x740 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] l2cap_chan_create+0x41/0x340 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+0x4af/0x8b0 net/bluetooth/6lowpan.c:1090 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Freed by task 7741: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 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+0x48a/0x8b0 net/bluetooth/6lowpan.c:1087 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 The buggy address belongs to the object at ffff88809e502340 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff88809e502340, ffff88809e502b40) The buggy address belongs to the page: page:ffffea0002794080 count:1 mapcount:0 mapping:ffff88812c29cc40 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffffea0002794588 ffffea00027bab88 ffff88812c29cc40 raw: 0000000000000000 ffff88809e502340 0000000100000003 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809e502200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88809e502280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88809e502300: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff88809e502380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809e502400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================