bisecting fixing commit since f25804f389846835535db255e7ba80eeed967ed7 building syzkaller on c88c7b75a4e022b758f4b0f1bf3db8ebb2fb25e6 testing commit f25804f389846835535db255e7ba80eeed967ed7 with gcc (GCC) 8.1.0 kernel signature: 53e6fe632fb6727cdc8d7600246c2e0b2faf0cbeaa149e79a907269795d940f8 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 Read in l2cap_chan_close run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close 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 Read in l2cap_chan_close testing current HEAD 54b4fa6d39551639cb10664f6ac78b01993a1d7e testing commit 54b4fa6d39551639cb10664f6ac78b01993a1d7e with gcc (GCC) 8.1.0 kernel signature: 97b9a406f9e85721c3d81a6edc2ac0db65d0fcc432d2b1f45e59d67465e1de0a 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 Read in l2cap_chan_close 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 Write in ex_handler_refcount run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close revisions tested: 2, total time: 24m38.453817452s (build: 17m49.357307103s, test: 6m13.772676513s) the crash still happens on HEAD commit msg: Linux 4.19.113 crash: KASAN: use-after-free Read in l2cap_chan_close 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+0x536/0x830 net/bluetooth/l2cap_core.c:727 Read of size 1 at addr ffff88809c97c960 by task kworker/1:2/2860 CPU: 1 PID: 2860 Comm: kworker/1:2 Not tainted 4.19.113-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 7777: 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 7777: 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 ffff88809c97c940 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff88809c97c940, ffff88809c97d140) The buggy address belongs to the page: page:ffffea0002725f00 count:1 mapcount:0 mapping:ffff88812c29cc40 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffffea00021dc808 ffffea0002780388 ffff88812c29cc40 raw: 0000000000000000 ffff88809c97c0c0 0000000100000003 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809c97c800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88809c97c880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88809c97c900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff88809c97c980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809c97ca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================