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[PATCH][RFC] XFS: Fix mem leak and possible NULL deref in xfs_setattr_no

To: xfs@xxxxxxxxxxx
Subject: [PATCH][RFC] XFS: Fix mem leak and possible NULL deref in xfs_setattr_nonsize()
From: Jesper Juhl <jj@xxxxxxxxxxxxx>
Date: Sun, 5 Feb 2012 22:23:44 +0100 (CET)
Cc: xfs-masters@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Ben Myers <bpm@xxxxxxx>, Alex Elder <elder@xxxxxxxxxx>
User-agent: Alpine 2.00 (LNX 1167 2008-08-23)
In xfs_setattr_nonsize(), xfs_trans_alloc() gets its memory from
_xfs_trans_alloc() which gets it from kmem_zone_zalloc() which may
fail and return NULL. So this:

        tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_NOT_SIZE);

may result in a NULL 'tp'.
If it does, then the call:

        error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0);

with a NULL 'tp' will explode, since xfs_trans_reserve() dereferences
its first argument unconditionally.

And if the memory allocation for 'tp' goes well (and thus
xfs_trans_reserve() does not explode) then we may leak the memory
allocated to 'tp' if xfs_trans_reserve() returns error.

I believe this patch should fix both issues, but I'm not intimate with
the XFS code at all, so there can easily be something I overlooked or
something that should be done differently than what I did.

Signed-off-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_iops.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

 Note:
  Please review carefully before applying.
  Especially since I don't currently have any XFS filesystems to test
  this on, nor any clear idea of a good way to actually test this if I
  had. So this patch is compile tested only on my end.

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index ab30253..194c9d7 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -575,9 +575,14 @@ xfs_setattr_nonsize(
        }
 
        tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_NOT_SIZE);
+       if (!tp)
+               goto out_dqrele;
+
        error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0);
-       if (error)
+       if (error) {
+               xfs_trans_cancel(tp, 0);
                goto out_dqrele;
+       }
 
        xfs_ilock(ip, XFS_ILOCK_EXCL);
 
-- 
1.7.9


Please CC me on replies.

-- 
Jesper Juhl <jj@xxxxxxxxxxxxx>       http://www.chaosbits.net/
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