syzbot

random: cc1: uninitialized urandom read (8 bytes read)
audit: type=1400 audit(1553322826.509:9): avc:  denied  { map } for  pid=1802 comm="syz-execprog" path="/root/syzkaller-shm925405876" dev="sda1" ino=16482 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:file_t:s0 tclass=file permissive=1
Can't find any breakpoint slot
------------[ cut here ]------------
WARNING: CPU: 0 PID: 2746 at arch/x86/kernel/hw_breakpoint.c:121 arch_install_hw_breakpoint.cold+0x13/0x1f arch/x86/kernel/hw_breakpoint.c:121
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 2746 Comm: syz-executor.2 Not tainted 4.14.107+ #34
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 panic+0x1d9/0x3c2 kernel/panic.c:182
 __warn.cold+0x2f/0x3b kernel/panic.c:546

======================================================
WARNING: possible circular locking dependency detected
4.14.107+ #34 Not tainted
------------------------------------------------------
syz-executor.2/2746 is trying to acquire lock:
 ((console_sem).lock){-...}, at: [<ffffffffa8beff9e>] down_trylock+0xe/0x60 kernel/locking/semaphore.c:136

but task is already holding lock:
 (&ctx->lock){....}, at: [<ffffffffa8df85f5>] perf_ctx_lock kernel/events/core.c:157 [inline]
 (&ctx->lock){....}, at: [<ffffffffa8df85f5>] perf_event_context_sched_in kernel/events/core.c:3265 [inline]
 (&ctx->lock){....}, at: [<ffffffffa8df85f5>] __perf_event_task_sched_in+0x2a5/0x420 kernel/events/core.c:3323

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ctx->lock){....}:

-> #2 (&rq->lock){-.-.}:

-> #1 (&p->pi_lock){-.-.}:

-> #0 ((console_sem).lock){-...}:

other info that might help us debug this:

Chain exists of:
  (console_sem).lock --> &rq->lock --> &ctx->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ctx->lock);
                               lock(&rq->lock);
                               lock(&ctx->lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

2 locks held by syz-executor.2/2746:
 #0:  (&cpuctx_lock){....}, at: [<ffffffffa8df85e4>] perf_ctx_lock kernel/events/core.c:155 [inline]
 #0:  (&cpuctx_lock){....}, at: [<ffffffffa8df85e4>] perf_event_context_sched_in kernel/events/core.c:3265 [inline]
 #0:  (&cpuctx_lock){....}, at: [<ffffffffa8df85e4>] __perf_event_task_sched_in+0x294/0x420 kernel/events/core.c:3323
 #1:  (&ctx->lock){....}, at: [<ffffffffa8df85f5>] perf_ctx_lock kernel/events/core.c:157 [inline]
 #1:  (&ctx->lock){....}, at: [<ffffffffa8df85f5>] perf_event_context_sched_in kernel/events/core.c:3265 [inline]
 #1:  (&ctx->lock){....}, at: [<ffffffffa8df85f5>] __perf_event_task_sched_in+0x2a5/0x420 kernel/events/core.c:3323

stack backtrace:
CPU: 0 PID: 2746 Comm: syz-executor.2 Not tainted 4.14.107+ #34
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
Kernel Offset: 0x27a00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
Rebooting in 86400 seconds..