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Re: xfs_repair segfault

To: Viet Nguyen <vietnguyen@xxxxxxxxx>
Subject: Re: xfs_repair segfault
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sat, 5 Oct 2013 07:43:53 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <CAGa409_wO74zGP1d85RGZ7WbfBPr7s_tKaW3u9k8=9Ps-D5FjQ@xxxxxxxxxxxxxx>
References: <CAGa4098ZKd2KQfWMgNXYgLr9LJF8r-MpFgQAn3G-W+ovDGHTAw@xxxxxxxxxxxxxx> <20131001201909.GR12541@dastard> <CAGa409_tDjbsdnf+wDiM7666FeQSjmMfOVdqG-SxOD_WUZMiZQ@xxxxxxxxxxxxxx> <20131002104253.GT12541@dastard> <CAGa409_wO74zGP1d85RGZ7WbfBPr7s_tKaW3u9k8=9Ps-D5FjQ@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Oct 04, 2013 at 10:51:50AM -0700, Viet Nguyen wrote:
> Hi,
> 
> I was wondering if you got a chance to look at this and if one's available,
> where can I get a patch?

Can you try the patch below?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

libxfs: validity check the directory block leaf entry count

From: Dave Chinner <dchinner@xxxxxxxxxx>

The directory block format verifier fails to check that the leaf
entry count is in a valid range, and so if it is corrupted then it
can lead to derefencing a pointer outside the block buffer. While we
can't exactly validate the count without first walking the directory
block, we can ensure the count lands in the valid area within the
directory block and hence avoid out-of-block references.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 libxfs/xfs_dir2_data.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/libxfs/xfs_dir2_data.c b/libxfs/xfs_dir2_data.c
index 189699f..1b5196b 100644
--- a/libxfs/xfs_dir2_data.c
+++ b/libxfs/xfs_dir2_data.c
@@ -59,6 +59,18 @@ __xfs_dir3_data_check(
                btp = xfs_dir2_block_tail_p(mp, hdr);
                lep = xfs_dir2_block_leaf_p(btp);
                endp = (char *)lep;
+
+               /*
+                * The number of leaf entries is limited by the size of the
+                * block and the amount of space used by the data entries.
+                * We don't know how much space is used by the data entries yet,
+                * so just ensure that the count falls somewhere inside the
+                * block right now.
+                */
+               XFS_WANT_CORRUPTED_RETURN(be32_to_cpu(btp->count) >
+                               ((char *)btp - (char *)p) /
+                                       sizeof(struct xfs_dir2_leaf_entry));
+
                break;
        case cpu_to_be32(XFS_DIR3_DATA_MAGIC):
        case cpu_to_be32(XFS_DIR2_DATA_MAGIC):

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