bisecting fixing commit since 9b15f7fae677336e04b9e026ff91854e43165455 building syzkaller on 1ce142dcc7e25341405592c66bcb7cb0d60d2b3a testing commit 9b15f7fae677336e04b9e026ff91854e43165455 with gcc (GCC) 8.1.0 kernel signature: 7b6aa11af3bdf07a285f50c1c74f89ba2ae8642965986d18a28ea3d24c203a72 all runs: crashed: WARNING: bad unlock balance in ucma_destroy_id testing current HEAD a87f96283793d58b042618c689630db264715274 testing commit a87f96283793d58b042618c689630db264715274 with gcc (GCC) 8.1.0 kernel signature: 6c7fba5a32a7e9539e47ad3b3692a58f057e349372080b0cdd11c40fb0077eb3 all runs: crashed: WARNING: bad unlock balance in ucma_destroy_id revisions tested: 2, total time: 25m4.777364043s (build: 16m36.00564082s, test: 8m4.489706018s) the crash still happens on HEAD commit msg: Linux 4.19.145 crash: WARNING: bad unlock balance in ucma_destroy_id IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready ===================================== WARNING: bad unlock balance detected! 4.19.145-syzkaller #0 Not tainted ------------------------------------- syz-executor.1/18648 is trying to release lock (&file->mut) at: [] ucma_destroy_id+0x240/0x400 drivers/infiniband/core/ucma.c:631 but there are no more locks to release! other info that might help us debug this: 1 lock held by syz-executor.1/18648: #0: 000000006ea3c2a1 (&file->mut){+.+.}, at: ucma_destroy_id+0x1e0/0x400 drivers/infiniband/core/ucma.c:629 stack backtrace: CPU: 1 PID: 18648 Comm: syz-executor.1 Not tainted 4.19.145-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x123/0x177 lib/dump_stack.c:118 print_unlock_imbalance_bug.cold.50+0x114/0x123 kernel/locking/lockdep.c:3468 __lock_release kernel/locking/lockdep.c:3678 [inline] lock_release+0x685/0x850 kernel/locking/lockdep.c:3926 __mutex_unlock_slowpath+0x8e/0x6a0 kernel/locking/mutex.c:1197 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:713 ucma_destroy_id+0x240/0x400 drivers/infiniband/core/ucma.c:631 ucma_write+0x203/0x2d0 drivers/infiniband/core/ucma.c:1734 __vfs_write+0xe3/0x890 fs/read_write.c:485 vfs_write+0x150/0x4d0 fs/read_write.c:549 ksys_write+0x103/0x260 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:608 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c739 Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fa3963fbc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fa3963fc6d4 RCX: 000000000045c739 RDX: 0000000000000018 RSI: 0000000020001380 RDI: 0000000000000003 RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000c8a R14: 00000000004d7970 R15: 000000000076bfcc