bisecting fixing commit since 961f830af0658ef5ef8a7708786d634a6115f16b building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66 testing commit 961f830af0658ef5ef8a7708786d634a6115f16b with gcc (GCC) 8.4.1 20210217 kernel signature: d3b6dd27d7b7ab8e2ae247c6213ccdc4b36bf23356cf0f9839128ccb00e7a5bc run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #4: crashed: KASAN: use-after-free Read in lock_sock_nested run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #8: crashed: KASAN: use-after-free Read in lock_sock_nested run #9: crashed: KASAN: use-after-free Read in lock_sock_nested run #10: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #11: crashed: KASAN: use-after-free Read in lock_sock_nested run #12: crashed: KASAN: use-after-free Read in lock_sock_nested run #13: crashed: KASAN: use-after-free Read in lock_sock_nested run #14: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #15: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #16: crashed: KASAN: use-after-free Read in lock_sock_nested run #17: crashed: KASAN: use-after-free Read in lock_sock_nested run #18: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #19: crashed: KASAN: use-after-free Read in lock_sock_nested testing current HEAD 2965db2e004cf9c92b87c1f559e9812c0ae878c1 testing commit 2965db2e004cf9c92b87c1f559e9812c0ae878c1 with gcc (GCC) 8.4.1 20210217 kernel signature: c77e2ad9b0a250b094050b27e9754874ff4d3e953fcdb3b96446113a9d307e44 run #0: crashed: KASAN: use-after-free Read in lock_sock_nested run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #3: crashed: KASAN: use-after-free Read in lock_sock_nested run #4: crashed: KASAN: use-after-free Read in lock_sock_nested run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #6: crashed: KASAN: use-after-free Read in lock_sock_nested run #7: crashed: KASAN: use-after-free Read in lock_sock_nested run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put run #9: crashed: KASAN: use-after-free Read in lock_sock_nested revisions tested: 2, total time: 37m49.627984659s (build: 26m41.473482533s, test: 10m31.39974272s) the crash still happens on HEAD commit msg: Linux 4.19.188 crash: KASAN: use-after-free Read in lock_sock_nested ================================================================== BUG: KASAN: use-after-free in __lock_acquire+0x31e7/0x47c0 kernel/locking/lockdep.c:3294 Read of size 8 at addr ffff8881d636eda0 by task kworker/1:3/6083 CPU: 1 PID: 6083 Comm: kworker/1:3 Not tainted 4.19.188-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events l2cap_chan_timeout Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report mm/kasan/report.c:412 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 __lock_acquire+0x31e7/0x47c0 kernel/locking/lockdep.c:3294 lock_acquire+0x180/0x3a0 kernel/locking/lockdep.c:3907 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh include/linux/spinlock.h:334 [inline] lock_sock_nested+0x3a/0x100 net/core/sock.c:2864 l2cap_sock_teardown_cb+0x87/0x400 net/bluetooth/l2cap_sock.c:1340 l2cap_chan_close+0x3ef/0x830 net/bluetooth/l2cap_core.c:761 l2cap_chan_timeout+0x11d/0x1c0 net/bluetooth/l2cap_core.c:430 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2152 worker_thread+0x85/0xb60 kernel/workqueue.c:2295 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Allocated by task 11961: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kmem_cache_alloc_trace+0x152/0x3a0 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:444 l2cap_sock_alloc.constprop.4+0x150/0x1e0 net/bluetooth/l2cap_sock.c:1632 l2cap_sock_create+0xb5/0x180 net/bluetooth/l2cap_sock.c:1663 bt_sock_create+0x121/0x260 net/bluetooth/af_bluetooth.c:130 __sock_create+0x262/0x540 net/socket.c:1276 sock_create net/socket.c:1316 [inline] __sys_socket+0xd7/0x1d0 net/socket.c:1346 __do_sys_socket net/socket.c:1355 [inline] __se_sys_socket net/socket.c:1353 [inline] __x64_sys_socket+0x6e/0xb0 net/socket.c:1353 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 11934: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 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 net/bluetooth/l2cap_core.c:482 [inline] kref_put include/linux/kref.h:70 [inline] l2cap_chan_put+0x141/0x1a0 net/bluetooth/l2cap_core.c:496 l2cap_sock_release+0x1c1/0x240 net/bluetooth/l2cap_sock.c:1212 __sock_release+0xc2/0x290 net/socket.c:579 sock_close+0x10/0x20 net/socket.c:1140 __fput+0x249/0x7f0 fs/file_table.c:278 ____fput+0x9/0x10 fs/file_table.c:309 task_work_run+0x108/0x180 kernel/task_work.c:113 get_signal+0x1352/0x1970 kernel/signal.c:2400 do_signal+0x87/0x1870 arch/x86/kernel/signal.c:799 exit_to_usermode_loop+0x159/0x1e0 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8881d636ed00 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 160 bytes inside of 2048-byte region [ffff8881d636ed00, ffff8881d636f500) The buggy address belongs to the page: page:ffffea000758db80 count:1 mapcount:0 mapping:ffff8881f6400c40 index:0x0 compound_mapcount: 0 flags: 0x17ffe0000008100(slab|head) raw: 017ffe0000008100 ffffea000759c788 ffffea0007622e08 ffff8881f6400c40 raw: 0000000000000000 ffff8881d636e480 0000000100000003 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881d636ec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881d636ed00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881d636ed80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881d636ee00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881d636ee80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. CPU: 1 PID: 6083 Comm: kworker/1:3 Tainted: G B 4.19.188-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events l2cap_chan_timeout Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 assign_lock_key kernel/locking/lockdep.c:727 [inline] register_lock_class+0x1905/0x1b10 kernel/locking/lockdep.c:753 __lock_acquire+0x1a0/0x47c0 kernel/locking/lockdep.c:3303 lock_acquire+0x180/0x3a0 kernel/locking/lockdep.c:3907 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh include/linux/spinlock.h:334 [inline] lock_sock_nested+0x3a/0x100 net/core/sock.c:2864 l2cap_sock_teardown_cb+0x87/0x400 net/bluetooth/l2cap_sock.c:1340 l2cap_chan_close+0x3ef/0x830 net/bluetooth/l2cap_core.c:761 l2cap_chan_timeout+0x11d/0x1c0 net/bluetooth/l2cap_core.c:430 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2152 worker_thread+0x85/0xb60 kernel/workqueue.c:2295 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415