bisecting fixing commit since 63623fd44972d1ed2bfb6e0fb631dfcf547fd1e7 building syzkaller on c88c7b75a4e022b758f4b0f1bf3db8ebb2fb25e6 testing commit 63623fd44972d1ed2bfb6e0fb631dfcf547fd1e7 with gcc (GCC) 8.1.0 kernel signature: d3b2e7bd2e38c50d3f03145a6e9bc6060744fe3a2eaeba39249c993e2f66b551 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: WARNING: refcount bug in l2cap_chan_put run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: crashed: WARNING: refcount bug in l2cap_chan_put run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close run #8: crashed: WARNING: refcount bug in l2cap_chan_put run #9: crashed: WARNING: refcount bug in l2cap_chan_put testing current HEAD 8632e9b5645bbc2331d21d892b0d6961c1a08429 testing commit 8632e9b5645bbc2331d21d892b0d6961c1a08429 with gcc (GCC) 8.1.0 kernel signature: a8a9b29d96add811c845c9a42c564bad2a984d15be6000192fde6e2372493712 run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close run #1: crashed: WARNING: refcount bug in l2cap_chan_put 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: WARNING: refcount bug in l2cap_chan_put 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: WARNING: refcount bug in l2cap_chan_put 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: 20m15.986291835s (build: 12m6.606659641s, test: 7m15.097417896s) the crash still happens on HEAD commit msg: Merge tag 'hyperv-fixes-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux crash: KASAN: use-after-free Read in l2cap_chan_close ================================================================== BUG: KASAN: use-after-free in l2cap_chan_close+0x726/0xc80 net/bluetooth/l2cap_core.c:794 Read of size 1 at addr ffff88809d7c8020 by task kworker/0:2/45 CPU: 0 PID: 45 Comm: kworker/0:2 Not tainted 5.7.0-rc1-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 2940: 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 2940: 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 ffff88809d7c8000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 32 bytes inside of 2048-byte region [ffff88809d7c8000, ffff88809d7c8800) The buggy address belongs to the page: page:ffffea000275f200 refcount:1 mapcount:0 mapping:000000006a2a74c8 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea000238c508 ffffea000276fac8 ffff8880aa400e00 raw: 0000000000000000 ffff88809d7c8000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809d7c7f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88809d7c7f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88809d7c8000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88809d7c8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809d7c8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================