====================================================== WARNING: possible circular locking dependency detected 4.14.112+ #58 Not tainted ------------------------------------------------------ syz-executor.3/24376 is trying to acquire lock: (&mm->mmap_sem){++++}, at: [<00000000635330c8>] __might_fault+0xd4/0x1b0 mm/memory.c:4577 but task is already holding lock: (&cpuctx_mutex){+.+.}, at: [<00000000bfab347d>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1240 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&cpuctx_mutex){+.+.}: -> #4 (pmus_lock){+.+.}: -> #3 (cpu_hotplug_lock.rw_sem){++++}: -> #2 (&sb->s_type->i_mutex_key#10){+.+.}: -> #1 (ashmem_mutex){+.+.}: -> #0 (&mm->mmap_sem){++++}: other info that might help us debug this: Chain exists of: &mm->mmap_sem --> pmus_lock --> &cpuctx_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&cpuctx_mutex); lock(pmus_lock); lock(&cpuctx_mutex); lock(&mm->mmap_sem); *** DEADLOCK *** 1 lock held by syz-executor.3/24376: #0: (&cpuctx_mutex){+.+.}, at: [<00000000bfab347d>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1240 stack backtrace: CPU: 1 PID: 24376 Comm: syz-executor.3 Not tainted 4.14.112+ #58 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xb9/0x10e lib/dump_stack.c:53 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258