linux-kernel - Re: [PATCH] AFS: Stop readlink() on AFS crashing because file not passed to afs

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Date:	Fri, 28 Aug 2009 15:01:18 +0100
From:	David Howells <dhowells@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	dhowells@...hat.com, torvalds@...ux-foundation.org,
	linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
	anton@...ba.org, stable@...nel.org
Subject: Re: [PATCH] AFS: Stop readlink() on AFS crashing because file not passed to afs_readpage()

Andrew Morton <akpm@...ux-foundation.org> wrote:

> That seems like a rather large bug.

Indeed.

I've not seen this happen because when a symlink inode is filled in,
afs_mntpt_check_symlink() is called to see whether it's actually a mountpoint,
and *that* calls read_mapping_page() correctly to read the contents of the
symlink.

The contents of the symlink then hang around in the pagecache, preventing
further calls to afs_readpage() by page_getlink().

However, if you wait long enough, as presumably Anton has, the contents of the
symlink get ejected from the pagecache, but the inode is retained, and thus
the next readlink will oops.

> To which kernel version(s) should we apply this?

kAFS isn't that widely used yet, so only the latest, I think.

David
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