linux-kernel - Re: BUG: 2.6.26-rc1-git8: NULL reference in drop

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Message-ID: <48285C94.6070204@oracle.com>
Date:	Mon, 12 May 2008 08:04:52 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	lkml <linux-kernel@...r.kernel.org>,
	viro <viro@...iv.linux.org.uk>, Jan Kara <jack@....cz>,
	linux-mm@...ck.org
Subject: Re: BUG: 2.6.26-rc1-git8: NULL reference in drop_buffers

Andrew Morton wrote:
> On Sun, 11 May 2008 10:54:29 -0700 Randy Dunlap <randy.dunlap@...cle.com> wrote:
> 
>> On x86_64, during testing using "stress" package:
>>
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> 
> 
>> IP: [<ffffffff802ad273>] drop_buffers+0x2f/0xfb
>> PGD 1ee8ad067 PUD 26f19a067 PMD 0
>> Oops: 0000 [1] SMP
>> CPU 3
>> Modules linked in: parport_pc lp parport tg3 cciss ehci_hcd ohci_hcd uhci_hcd
>> Pid: 16860, comm: stress Not tainted 2.6.26-rc1-git8 #1
>> RIP: 0010:[<ffffffff802ad273>]  [<ffffffff802ad273>] drop_buffers+0x2f/0xfb
>> RSP: 0000:ffff81026bc03a08  EFLAGS: 00010203
>> RAX: 0000000000000000 RBX: ffffe20008bae680 RCX: ffff81027f490f00
>> RDX: 0000000000000000 RSI: ffff81026bc03a58 RDI: ffffe20008bae680
>> RBP: ffff81026bc03a38 R08: ffff81026bc03b78 R09: ffff810001103780
>> R10: ffff81026bc03a08 R11: ffff81026bc03c88 R12: ffffe20008bae680
>> R13: ffff81027c412850 R14: ffff81026bc03d58 R15: ffff81026bc03a58
>> FS:  00007fa9e7e416f0(0000) GS:ffff81027f806980(0000) knlGS:00000000f7f856c0
>> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>> CR2: 0000000000000000 CR3: 000000027f973000 CR4: 00000000000006e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>> Process stress (pid: 16860, threadinfo ffff81026bc02000, task ffff81027e424c50)
>> Stack:  ffffe20008bafa68 ffffe20008bae680 ffff81027f490f00 ffff81026bc03a58
>>  ffff81026bc03d58 ffff81026bc03c88 ffff81026bc03a78 ffffffff802ad39f
>>  ffff81027f490f00 ffffe20008b14060 0000000000000000 ffff81027f490f00
>> Call Trace:
>>  [<ffffffff802ad39f>] try_to_free_buffers+0x60/0xa2
>>  [<ffffffff80267f98>] try_to_release_page+0x3b/0x41
>>  [<ffffffff802719bc>] shrink_page_list+0x457/0x562
>>  [<ffffffff80271bed>] shrink_inactive_list+0x126/0x361
>>  [<ffffffff80271f0d>] shrink_zone+0xe5/0x10a
>>  [<ffffffff8027227d>] try_to_free_pages+0x1ef/0x326
>>  [<ffffffff80270f4b>] ? isolate_pages_global+0x0/0x34
>>  [<ffffffff8026d843>] __alloc_pages_internal+0x25a/0x3ad
>>  [<ffffffff8026d9ac>] __alloc_pages+0xb/0xd
>>  [<ffffffff80277759>] handle_mm_fault+0x238/0x6d0
>>  [<ffffffff8053d9c4>] do_page_fault+0x438/0x7de
>>  [<ffffffff8053b999>] error_exit+0x0/0x51
>>
>>
>> Code: 41 57 49 89 f7 41 56 41 55 41 54 49 89 fc 53 48 83 ec 08 48 8b 07 25 00 08 00 00 48 85 c0 75 04 0f 0b eb fe 4c 8b 6f 10 4c 89 ea <48> 8b 02 25 00 08 00 00 48 85 c0 74 10 49 8b 44 24 18 48 85 c0
>> RIP  [<ffffffff802ad273>] drop_buffers+0x2f/0xfb
>>  RSP <ffff81026bc03a08>
>> CR2: 0000000000000000
>> Kernel panic - not syncing: Fatal exception
> 
> Seems that local variable `bh' is NULL.
> 
> I wonder what the heck we did to cause that.  Which filesystems were in
> use?

ext3, nfs, and the usual procfs, sysfs, and tmpfs.

Also in the kernel:  debugfs, usbfs, inotifyfs, configfs, ramfs,
hugetlbfs, msdos, vfat, iso9660, and rootfs.

-- 
~Randy
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