Re: locks_get_lock_context null deref

[William Dauchy <william@gandi.net>]

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Hi Jeff,

After a few days of testing, I was unable to reproduce the null deref
mentionned in this thread.
Do you think we can ask for a backport in stable@ for v4.1?

bcd7f78 locks: have flock_lock_file take an inode pointer instead of a filp
29d01b2 locks: new helpers - flock_lock_inode_wait and posix_lock_inode_wait
ee296d7 locks: inline posix_lock_file_wait and flock_lock_file_wait
83bfff2 nfs4: have do_vfs_lock take an inode pointer

On Oct19 19:40, William Dauchy wrote:
> On Oct19 18:33, William Dauchy wrote:
> > I am getting the following null deref on locks_get_lock_context using a v4.1.x
> > (x86_64) while using the nfs client v4.0.
> > 
> > Any hint to help debug that issue?
> > 
> > 
> > BUG: unable to handle kernel NULL pointer dereference at 00000000000001c8
> > IP: [<ffffffff811d0cf3>] locks_get_lock_context+0x3/0xc0
> > PGD 0 
> > Oops: 0000 [#1] SMP 
> > CPU: 1 PID: 1773 Comm: kworker/1:1H Not tainted 4.1.11-rc1 #1
> > Workqueue: rpciod ffffffff8164fff0
> > task: ffff8810374deba0 ti: ffff8810374df150 task.ti: ffff8810374df150
> > RIP: 0010:[<ffffffff811d0cf3>]  [<ffffffff811d0cf3>] locks_get_lock_context+0x3/0xc0
> > RSP: 0000:ffff881036007bb0  EFLAGS: 00010246
> > RAX: ffff881036007c30 RBX: ffff881001981880 RCX: 0000000000000002
> > RDX: 00000000000006ed RSI: 0000000000000002 RDI: 0000000000000000
> > RBP: ffff881036007c08 R08: 0000000000000000 R09: 0000000000000001
> > R10: 0000000000000000 R11: ffff88101db69948 R12: ffff8810019818d8
> > R13: ffff881036007bc8 R14: ffff880e225d81c0 R15: ffff881edfd2b400
> > FS:  0000000000000000(0000) GS:ffff88103fc20000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000000001c8 CR3: 000000000169b000 CR4: 00000000000606f0
> > Stack:
> >  ffffffff811d2710 ffff881036007bc8 ffffffff819f1af1 ffff881036007bc8
> >  ffff881036007bc8 ffff881036007c08 ffff881001981880 ffff8810019818d8
> >  ffff881036007c48 ffff880e225d81c0 ffff881edfd2b400 ffff881036007c88
> > Call Trace:
> >  [<ffffffff811d2710>] ? flock_lock_file+0x30/0x270
> >  [<ffffffff811d3ad1>] flock_lock_file_wait+0x41/0xf0
> >  [<ffffffff8168be66>] ? _raw_spin_unlock+0x26/0x40
> >  [<ffffffff81268de9>] do_vfs_lock+0x19/0x40
> >  [<ffffffff812695cc>] nfs4_locku_done+0x5c/0xf0
> >  [<ffffffff8164f3f4>] rpc_exit_task+0x34/0xb0
> >  [<ffffffff8164fcd9>] __rpc_execute+0x79/0x390
> >  [<ffffffff81650000>] rpc_async_schedule+0x10/0x20
> >  [<ffffffff81086095>] process_one_work+0x1a5/0x450
> >  [<ffffffff81086024>] ? process_one_work+0x134/0x450
> >  [<ffffffff8108638b>] worker_thread+0x4b/0x4a0
> >  [<ffffffff81086340>] ? process_one_work+0x450/0x450
> >  [<ffffffff81086340>] ? process_one_work+0x450/0x450
> >  [<ffffffff8108d777>] kthread+0xf7/0x110
> >  [<ffffffff8108d680>] ? __kthread_parkme+0xa0/0xa0
> >  [<ffffffff8168ce3e>] ret_from_fork+0x3e/0x70
> >  [<ffffffff8108d680>] ? __kthread_parkme+0xa0/0xa0
> > Code: 48 b8 00 00 00 00 00 00 00 80 55 48 89 e5 48 09 c1 ff d1 5d 85 c0 0f 95 c0 0f b6 c0 eb b9 66 2e 0f 1f 84 00 00 00 00 00 83 fe 02 <48> 8b 87 c8 01 00 00 0f 84 a0 00 00 00 48 85 c0 0f 85 97 00 00 
> > RIP  [<ffffffff811d0cf3>] locks_get_lock_context+0x3/0xc0
> >  RSP <ffff881036007bb0>
> > CR2: 00000000000001c8
> > ---[ end trace 2da9686dda1b5574 ]---
> 
> As mentioned in another thread by Jeff, I applied the following commits:
> 
> bcd7f78 locks: have flock_lock_file take an inode pointer instead of a filp
> 29d01b2 locks: new helpers - flock_lock_inode_wait and posix_lock_inode_wait
> ee296d7 locks: inline posix_lock_file_wait and flock_lock_file_wait
> 83bfff2 nfs4: have do_vfs_lock take an inode pointer
> 
> I will see if I get the same issue again.

-- 
William

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