From: "Darrick J. Wong" <djwong@us.ibm.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ext4: Fix 'return 0' for error case in ext4_fill_super
Date: Thu, 18 Nov 2010 14:21:57 -0800 [thread overview]
Message-ID: <20101118222157.GE18195@tux1.beaverton.ibm.com> (raw)
In-Reply-To: <1290116832-29443-1-git-send-email-joro@8bytes.org>
On Thu, Nov 18, 2010 at 10:47:12PM +0100, Joerg Roedel wrote:
> The ext4_fill_super may return with value 0 in case of an error. The
> reason is that the ret variable is used to store the return value of a
> called function and is not set back to an error value later on.
> This issue caused a NULL pointer de-ref in vfs_kern_mount on one of my
> machines when it tried to mount a partition:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
> IP: [<ffffffff8112e8dc>] vfs_kern_mount+0x7c/0x180
> PGD 218480067 PUD 225323067 PMD 0
> Oops: 0000 [#1] SMP
> last sysfs file: /sys/devices/system/cpu/cpu5/cache/index2/shared_cpu_map
> CPU 1
>
> ...
>
> Process mount (pid: 3591, threadinfo ffff8802258fc000, task ffff88022586dac0)
> Stack:
> ffff8802258fde38 0000000000000000 ffff880225e299b0 ffff880200000001
> ffffffff81a230e0 ffff880225e2c818 ffff8802258fde88 ffffffff8112ea52
> ffff8802258fde98 0000000000000246 ffff88022586dac0 0000000000000060
> Call Trace:
> [<ffffffff8112ea52>] do_kern_mount+0x52/0x130
> [<ffffffff811497ff>] do_mount+0x2bf/0x810
> [<ffffffff810face3>] ? strndup_user+0x53/0x70
> [<ffffffff81149de0>] sys_mount+0x90/0xe0
> [<ffffffff81002fdb>] system_call_fastpath+0x16/0x1b
>
> This patch fixes the issue by using the 'err' variable instead of 'ret'
> for that function-call like it is done in for all other function-calls
> in ext4_fill_super too.
> If have seen this issue on 2.6.36 too, so this patch may be -stable
> material as well.
Lukas and I have been trying to fix this bug for a couple of days now, and he
actually sent off an identical patch this morning:
http://www.spinics.net/lists/linux-ext4/msg21743.html
(I also sent off a similar cleanup of the ext3 counterpart.)
But, thanks for pointing this out! :)
--D
next prev parent reply other threads:[~2010-11-18 22:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-18 21:47 [PATCH] ext4: Fix 'return 0' for error case in ext4_fill_super Joerg Roedel
2010-11-18 22:21 ` Darrick J. Wong [this message]
2010-11-18 22:38 ` Joerg Roedel
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