[xfs-masters] [RFC][PATCH] XFS: memory leak in xfs_inactive() - is xfs_trans_free() enough or do we need xfs_trans_cancel() ?

[Jesper Juhl <jesper.juhl@xxxxxxxxx>]

Hi,

The Coverity checker found a memory leak in xfs_inactive().

The offending code is this bit : 

1671            tp = xfs_trans_alloc(mp, XFS_TRANS_INACTIVE);

At conditional (1): "truncate != 0" taking true path

1672            if (truncate) {
1673                    /*
1674                     * Do the xfs_itruncate_start() call before
1675                     * reserving any log space because itruncate_start
1676                     * will call into the buffer cache and we can't
1677                     * do that within a transaction.
1678                     */
1679                    xfs_ilock(ip, XFS_IOLOCK_EXCL);
1680    
1681                    error = xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE, 0);

At conditional (2): "error != 0" taking true path

1682                    if (error) {
1683                            xfs_iunlock(ip, XFS_IOLOCK_EXCL);

Event leaked_storage: Returned without freeing storage "tp"
Also see events: [alloc_fn][var_assign]

1684                            return VN_INACTIVE_CACHE;
1685                    }

So, the code allocates a transaction, but in the case where 'truncate' is !=0 
and xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE, 0); happens to return an 
error, we'll just return from the function without dealing with the memory 
allocated byxfs_trans_alloc() and assigned to 'tp', thus it'll be 
orphaned/leaked - not good.

What I'm wondering is this; is it enough, at this point, to call 
xfs_trans_free(tp); (it would seem to me that would be OK, but I'm not intimite 
with this code) or do we need a full xfs_trans_cancel(tp, 0);  ???

In case I'm right and xfs_trans_free(tp); is all we need, then please consider 
the patch below. Otherwise please NACK the patch and I'll cook up another one 
:-)


Fix memory leak on error in xfs_inactive().

Signed-off-by: Jesper Juhl <jesper.juhl@xxxxxxxxx>
--- 
 fs/xfs/xfs_vnodeops.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index de17aed..e0d3d51 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -1681,6 +1681,7 @@ xfs_inactive(
                error = xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE, 0);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+                       xfs_trans_free(tp);
                        return VN_INACTIVE_CACHE;
                }
 


-- 
Jesper Juhl <jesper.juhl@xxxxxxxxx>
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