I've been able to trigger this for the last week or so.
Unclear whether this is a new bug, or my fuzzer got smarter, but I see the
pi-futex code hasn't changed since the last time it found something..
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> IP: [<ffffffff810e185e>] __lock_acquire+0x5e/0x1ba0
> PGD 8e72c067 PUD 34f07067 PMD 0
> Oops: 0000 [#1] PREEMPT SMP
> CPU 7
> Pid: 27513, comm: trinity-child0 Not tainted 3.7.0-rc2+ #43
> RIP: 0010:[<ffffffff810e185e>] [<ffffffff810e185e>]
> __lock_acquire+0x5e/0x1ba0
> RSP: 0018:ffff8800803f7b28 EFLAGS: 00010046
> RAX: 0000000000000086 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018
> RBP: ffff8800803f7c18 R08: 0000000000000002 R09: 0000000000000000
> R10: 0000000000000000 R11: 2222222222222222 R12: 0000000000000002
> R13: ffff880051dd8000 R14: 0000000000000002 R15: 0000000000000018
> FS: 00007f9fc6ccb740(0000) GS:ffff880148a00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000018 CR3: 000000008e6fb000 CR4: 00000000001407e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process trinity-child0 (pid: 27513, threadinfo ffff8800803f6000, task
> ffff880051dd8000)
> Stack:
> ffff8800803f7b48 ffffffff816c5c59 ffff8800803f7b48 ffff88014840ebc0
> ffff8800803f7b68 ffffffff816c18e3 ffff8800803f7d10 0000000000000001
> ffff8800803f7ba8 ffffffff810a1e62 ffff8800803f7d10 0000000000000282
> Call Trace:
> [<ffffffff816c5c59>] ? sub_preempt_count+0x79/0xd0
> [<ffffffff816c18e3>] ? _raw_spin_unlock_irqrestore+0x73/0xa0
> [<ffffffff810a1e62>] ? hrtimer_try_to_cancel+0x52/0x210
> [<ffffffff810eb9e5>] ? debug_rt_mutex_free_waiter+0x15/0x180
> [<ffffffff816c0107>] ? rt_mutex_slowlock+0x127/0x1b0
> [<ffffffff810b7039>] ? local_clock+0x89/0xa0
> [<ffffffff810e3ac2>] lock_acquire+0xa2/0x220
> [<ffffffff810e812c>] ? futex_lock_pi.isra.18+0x1cc/0x390
> [<ffffffff816c09e0>] _raw_spin_lock+0x40/0x80
> [<ffffffff810e812c>] ? futex_lock_pi.isra.18+0x1cc/0x390
> [<ffffffff810e812c>] futex_lock_pi.isra.18+0x1cc/0x390
> [<ffffffff810a1980>] ? update_rmtp+0x70/0x70
> [<ffffffff810e99e4>] do_futex+0x394/0xa50
> [<ffffffff8119ec43>] ? might_fault+0x53/0xb0
> [<ffffffff810ea12d>] sys_futex+0x8d/0x190
> [<ffffffff816ca288>] tracesys+0xe1/0xe6
> Code: d8 45 0f 45 e0 4c 89 75 f0 4c 89 7d f8 85 c0 0f 84 f8 00 00 00 8b 05
> 22 fe f3 00 49 89 ff 89 f3 41 89 d2 85 c0 0f 84 02 01 00 00 <49> 8b 07 ba 01
> 00 00 00 48 3d c0 81 06 82 44 0f 44 e2 83 fb 01
> RIP [<ffffffff810e185e>] __lock_acquire+0x5e/0x1ba0
> RSP <ffff8800803f7b28>
> CR2: 0000000000000018
It looks like we got all the way to lock_acquire with a NULL 'lock' somehow.
Darren, any idea how this could happen ?
Dave
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