linux-kernel - Re: [RFC][PATCH] XFS: memory leak in xfs_inactive() - is xfs_trans_free() enough or do we need xfs_trans

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Date:	Thu, 17 May 2007 12:40:24 +1000
From:	David Chinner <dgc@....com>
To:	Jesper Juhl <jesper.juhl@...il.com>
Cc:	xfs-masters@....sgi.com, xfs@....sgi.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] XFS: memory leak in xfs_inactive() - is xfs_trans_free() enough or do we need xfs_trans_cancel() ?

On Wed, May 16, 2007 at 11:31:16PM +0200, Jesper Juhl wrote:
> Hi,
> 
> The Coverity checker found a memory leak in xfs_inactive().
....
> 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.

Yeah, introduced by:

http://git2.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d3cf209476b72c83907a412b6708c5e498410aa7

Thanks for reporting the problem, Jesper.

> 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);  ???

xfs_trans_free() is not supposed to be called by anything but the transaction
code (it's static). So a xfs_trans_cancel() would need to be issued.

> 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 :-)

NACK ;)

xfs_trans_cancel() is needed. Patch below.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group

---
 fs/xfs/xfs_vnodeops.c |    1 +
 1 file changed, 1 insertion(+)

Index: 2.6.x-xfs-new/fs/xfs/xfs_vnodeops.c
===================================================================
--- 2.6.x-xfs-new.orig/fs/xfs/xfs_vnodeops.c	2007-05-11 16:04:03.000000000 +1000
+++ 2.6.x-xfs-new/fs/xfs/xfs_vnodeops.c	2007-05-17 12:37:25.671399078 +1000
@@ -1710,6 +1710,7 @@ xfs_inactive(
 
 		error = xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE, 0);
 		if (error) {
+			xfs_trans_cancel(tp, 0);
 			xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 			return VN_INACTIVE_CACHE;
 		}
-
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