Re: 2.6.25-$sha1: RIP call_for_each_cic+0x25/0x50

[Jens Axboe]

On Mon, Apr 28 2008, Andrew Morton wrote:
> On Mon, 28 Apr 2008 02:55:53 +0400 Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote:
> 
> > This happened while ~90 cross-compile jobs were running in parallel on
> > ext2/noatime partition (slowly -- much debugging was on)
> > 
> > 
> > general protection fault: 0000 [1] PREEMPT SMP DEBUG_PAGEALLOC
> > CPU 0 
> > Modules linked in: ext2 nf_conntrack_irc ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack iptable_filter ip_tables x_tables usblp uhci_hcd ehci_hcd usbcore sr_mod cdrom
> > Pid: 16483, comm: as Not tainted 2.6.25-c3bf9bc243092c53946fd6d8ebd6dc2f4e572d48 #1
> > RIP: 0010:[<ffffffff80307525>]  [<ffffffff80307525>] call_for_each_cic+0x25/0x50
> > RSP: 0018:ffff810170811e58  EFLAGS: 00010202
> > RAX: 6b6b6b6b6b6b6b6b RBX: 6b6b6b6b6b6b6b6b RCX: 0000000000000000
> > RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff81010ff92000
> > RBP: ffff810170811e78 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000000 R11: ffff8100010069d8 R12: ffff810138ada300
> > R13: ffffffff803075b0 R14: ffff81017fcd2000 R15: ffff81010ff92168
> > FS:  00002ac3462426f0(0000) GS:ffffffff805d0000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > CR2: 00002ab602550000 CR3: 000000013609d000 CR4: 0000000000000660
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > Process as (pid: 16483, threadinfo ffff810170810000, task ffff81010ff92000)
> > Stack:  ffff810170811e88 ffff810138ada300 0000000000000010 ffff81010ff92100
> >  ffff810170811e88 ffffffff80307580 ffff810170811ea8 ffffffff80302a55
> >  ffff81010ff92100 ffff810138ada300 ffff810170811ec8 ffffffff80302b1f
> > Call Trace:
> >  [<ffffffff80307580>] cfq_free_io_context+0x10/0x20
> >  [<ffffffff80302a55>] put_io_context+0x85/0x90
> >  [<ffffffff80302b1f>] exit_io_context+0x8f/0xb0
> >  [<ffffffff80235d19>] do_exit+0x549/0x780
> >  [<ffffffff80235f8e>] do_group_exit+0x3e/0xb0
> >  [<ffffffff80236012>] sys_exit_group+0x12/0x20
> >  [<ffffffff8020b6db>] system_call_after_swapgs+0x7b/0x80
> > 
> > 
> > Code: 84 00 00 00 00 00 55 48 89 e5 41 55 49 89 f5 41 54 49 89 fc 53 48 83 ec 08 e8 18 e1 f5 ff 49 8b 44 24 68 48 85 c0 74 1e 48 89 c3 <48> 8b 03 48 8d 73 88 4c 89 e7 0f 18 08 41 ff d5 48 8b 03 48 85 
> > RIP  [<ffffffff80307525>] call_for_each_cic+0x25/0x50
> >  RSP <ffff810170811e58>
> > ---[ end trace ca143223eefdc828 ]---
> > Fixing recursive fault but reboot is needed!
> > 
> > 
> > ffffffff80307500 <call_for_each_cic>:
> > ffffffff80307500:	55                   	push   %rbp
> > ffffffff80307501:	48 89 e5             	mov    %rsp,%rbp
> > ffffffff80307504:	41 55                	push   %r13
> > ffffffff80307506:	49 89 f5             	mov    %rsi,%r13
> > ffffffff80307509:	41 54                	push   %r12
> > ffffffff8030750b:	49 89 fc             	mov    %rdi,%r12
> > ffffffff8030750e:	53                   	push   %rbx
> > ffffffff8030750f:	48 83 ec 08          	sub    $0x8,%rsp
> > ffffffff80307513:	e8 18 e1 f5 ff       	callq  ffffffff80265630 <__rcu_read_lock>
> > ffffffff80307518:	49 8b 44 24 68       	mov    0x68(%r12),%rax
> > ffffffff8030751d:	48 85 c0             	test   %rax,%rax
> > ffffffff80307520:	74 1e                	je     ffffffff80307540 <call_for_each_cic+0x40>
> > ffffffff80307522:	48 89 c3             	mov    %rax,%rbx
> > ffffffff80307525:	48 8b 03             	mov    (%rbx),%rax
> 
> use-after-free.

Yep, apparently a freed entry on the list. Not good...

> > ffffffff80307528:	48 8d 73 88          	lea    -0x78(%rbx),%rsi
> > ffffffff8030752c:	4c 89 e7             	mov    %r12,%rdi
> > ffffffff8030752f:	0f 18 08             	prefetcht0 (%rax)
> > ffffffff80307532:	41 ff d5             	callq  *%r13
> > ffffffff80307535:	48 8b 03             	mov    (%rbx),%rax
> > ffffffff80307538:	48 85 c0             	test   %rax,%rax
> > ffffffff8030753b:	48 89 c3             	mov    %rax,%rbx
> > ffffffff8030753e:	75 e5                	jne    ffffffff80307525 <call_for_each_cic+0x25>
> > ffffffff80307540:	e8 2b e0 f5 ff       	callq  ffffffff80265570 <__rcu_read_unlock>
> > ffffffff80307545:	48 83 c4 08          	add    $0x8,%rsp
> > ffffffff80307549:	5b                   	pop    %rbx
> > ffffffff8030754a:	41 5c                	pop    %r12
> > ffffffff8030754c:	41 5d                	pop    %r13
> > ffffffff8030754e:	c9                   	leaveq 
> > ffffffff8030754f:	c3                   	retq   
> 
> cfq-iosched.c hasn't been altered (yet) so it might not be a regression.

It's not a regression, it's definitely in 2.6.25 as well. So that's a
bit scary, I've been looking over this stuff this morning but haven't
pin pointed anything yet.

Alexey, is this something that reproduces for you?

-- 
Jens Axboe

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