bisecting fixing commit since f8788d86ab28f61f7b46eb6be375f8a726783636 building syzkaller on 59b57593586656c1d5be820aeed0e751087e6ac6 testing commit f8788d86ab28f61f7b46eb6be375f8a726783636 with gcc (GCC) 8.1.0 kernel signature: 3e85d72e0b555455db7ef3dd149e77a8ee862ea3bb48cf581ebfa48a2d532f2e run #0: crashed: WARNING: refcount bug in l2cap_chan_put run #1: crashed: WARNING: refcount bug in l2cap_chan_put run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close run #3: crashed: WARNING: refcount bug in l2cap_chan_put run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close run #5: crashed: WARNING: refcount bug in l2cap_chan_put run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close run #7: crashed: WARNING: refcount bug in l2cap_chan_put run #8: crashed: WARNING: refcount bug in l2cap_chan_put run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close testing current HEAD 51184ae37e0518fd90cb437a2fbc953ae558cd0d testing commit 51184ae37e0518fd90cb437a2fbc953ae558cd0d with gcc (GCC) 8.1.0 kernel signature: 0d178fb3fcf855e1b3d49b204e917f18392c297fba02b9837a6e58951d1b1ef3 run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close run #2: crashed: WARNING: refcount bug in l2cap_chan_put 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: WARNING: refcount bug in l2cap_chan_put 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: crashed: KASAN: use-after-free Read in l2cap_chan_close revisions tested: 2, total time: 21m41.281309574s (build: 13m2.629709242s, test: 7m41.093146468s) the crash still happens on HEAD commit msg: Merge tag 'for-5.7-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux 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 ================================================================== BUG: KASAN: use-after-free in l2cap_chan_close+0x726/0xc80 net/bluetooth/l2cap_core.c:794 Read of size 1 at addr ffff8880978b4020 by task kworker/0:9/2765 CPU: 0 PID: 2765 Comm: kworker/0:9 Not tainted 5.7.0-rc3-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+0x12d/0x187 lib/dump_stack.c:118 print_address_description.constprop.8.cold.10+0x9/0x31d mm/kasan/report.c:382 __kasan_report.cold.11+0x37/0x4e mm/kasan/report.c:511 kasan_report+0x38/0x50 mm/kasan/common.c:625 __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:143 l2cap_chan_close+0x726/0xc80 net/bluetooth/l2cap_core.c:794 do_enable_set+0x47e/0x8b0 net/bluetooth/6lowpan.c:1074 process_one_work+0x893/0x1690 kernel/workqueue.c:2268 worker_thread+0x85/0xb60 kernel/workqueue.c:2414 kthread+0x354/0x420 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Allocated by task 2765: save_stack+0x21/0x50 mm/kasan/common.c:49 set_track mm/kasan/common.c:57 [inline] __kasan_kmalloc.constprop.17+0xc7/0xd0 mm/kasan/common.c:495 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:509 kmem_cache_alloc_trace+0x15b/0x780 mm/slab.c:3551 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:669 [inline] l2cap_chan_create+0x41/0x360 net/bluetooth/l2cap_core.c:450 chan_create+0xa/0xc0 net/bluetooth/6lowpan.c:640 bt_6lowpan_listen net/bluetooth/6lowpan.c:959 [inline] do_enable_set+0x4af/0x8b0 net/bluetooth/6lowpan.c:1078 process_one_work+0x893/0x1690 kernel/workqueue.c:2268 worker_thread+0x85/0xb60 kernel/workqueue.c:2414 kthread+0x354/0x420 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Freed by task 2810: save_stack+0x21/0x50 mm/kasan/common.c:49 set_track mm/kasan/common.c:57 [inline] kasan_set_free_info mm/kasan/common.c:317 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:456 kasan_slab_free+0xe/0x10 mm/kasan/common.c:465 __cache_free mm/slab.c:3426 [inline] kfree+0x108/0x2c0 mm/slab.c:3757 l2cap_chan_destroy net/bluetooth/l2cap_core.c:488 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x15d/0x1d0 net/bluetooth/l2cap_core.c:502 do_enable_set+0x48a/0x8b0 net/bluetooth/6lowpan.c:1075 process_one_work+0x893/0x1690 kernel/workqueue.c:2268 worker_thread+0x85/0xb60 kernel/workqueue.c:2414 kthread+0x354/0x420 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 The buggy address belongs to the object at ffff8880978b4000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff8880978b4000, ffff8880978b4800) The buggy address belongs to the page: page:ffffea00025e2d00 refcount:1 mapcount:0 mapping:000000000fe39b42 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea00027df3c8 ffffea00024647c8 ffff8880aa400e00 raw: 0000000000000000 ffff8880978b4000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880978b3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880978b3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8880978b4000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880978b4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880978b4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================