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Re: [PATCH] xfs: catch invalid negative blknos in _xfs_buf_find()

To: Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: catch invalid negative blknos in _xfs_buf_find()
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Wed, 26 Nov 2014 10:38:05 -0600
Cc: xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <546D15E3.5000200@xxxxxxxxxx>
References: <546D15E3.5000200@xxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 11/19/14 16:12, Eric Sandeen wrote:
Here blkno is a daddr_t, which is a __s64; it's possible to hold
a value which is negative, and thus pass the (blkno>= eofs)
test.  Then we try to do a xfs_perag_get() for a ridiculous
agno via xfs_daddr_to_agno(), and bad things happen when that
fails, and returns a null pag which is dereferenced shortly
thereafter.

Found via a user-supplied fuzzed image...

Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
---

Looks good.

I did a little playing with sending the try lock failure (EAGAIN?) and EFSCORRUPT error status up the stack. It looked straight forward and could save a xfs_buf allocation when we know it is not necessary.

Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>

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