From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3] fs: don't scan the inode cache before SB_BORN is set
Date: Thu, 10 May 2018 20:09:16 +0100 [thread overview]
Message-ID: <20180510190916.GQ30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180510042132.GS23861@dastard>
On Thu, May 10, 2018 at 02:21:33PM +1000, Dave Chinner wrote:
> Setting sb->s_fs_info to NULL on xfs_mount setup failure only solves
> the use-after-free part of the problem - it doesn't solve the
> use-before-initialisation part. To solve that we need to check the
> SB_BORN flag in super_cache_count().
>
> The SB_BORN flag is not set until ->fs_mount() completes
> successfully and trylock_super() won't succeed until it is set.
> Hence super_cache_scan() will not run until SB_BORN is set, so it
> makes sense to not allow super_cache_scan to run and enter the
> filesystem until it is set, too. This prevents the superblock
> shrinker from entering the filesystem while it is being set up and
> so avoids the use-before-initialisation issue.
I'm fine with the first part of that (fs/super.c, that is), but
I don't understand why do you need the xfs side of the patch with
that. Confused...
next prev parent reply other threads:[~2018-05-10 19:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-10 4:21 [PATCH v3] fs: don't scan the inode cache before SB_BORN is set Dave Chinner
2018-05-10 16:39 ` Darrick J. Wong
2018-05-10 19:09 ` Al Viro [this message]
2018-05-10 23:55 ` Dave Chinner
2018-05-11 1:20 ` [PATCH v4] " Dave Chinner
2018-05-11 2:28 ` Al Viro
2018-05-11 3:04 ` Dave Chinner
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