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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Eric Sandeen" <sandeen@redhat.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        "Eric Sandeen" <sandeen@sandeen.net>, "Xu, Wen" <wen.xu@gatech.edu>
Date:   Sat, 22 Sep 2018 01:15:42 +0100
Message-ID: <lsq.1537575342.901442804@decadent.org.uk>
Subject: [PATCH 3.16 53/63] xfs: don't call xfs_da_shrink_inode with NULL bp
In-Reply-To: <lsq.1537575341.194909669@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.58-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@sandeen.net>

commit bb3d48dcf86a97dc25fe9fc2c11938e19cb4399a upstream.

xfs_attr3_leaf_create may have errored out before instantiating a buffer,
for example if the blkno is out of range.  In that case there is no work
to do to remove it, and in fact xfs_da_shrink_inode will lead to an oops
if we try.

This also seems to fix a flaw where the original error from
xfs_attr3_leaf_create gets overwritten in the cleanup case, and it
removes a pointless assignment to bp which isn't used after this.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199969
Reported-by: Xu, Wen <wen.xu@gatech.edu>
Tested-by: Xu, Wen <wen.xu@gatech.edu>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/xfs/xfs_attr_leaf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/xfs/xfs_attr_leaf.c
+++ b/fs/xfs/xfs_attr_leaf.c
@@ -701,9 +701,8 @@ xfs_attr_shortform_to_leaf(xfs_da_args_t
 	ASSERT(blkno == 0);
 	error = xfs_attr3_leaf_create(args, blkno, &bp);
 	if (error) {
-		error = xfs_da_shrink_inode(args, 0, bp);
-		bp = NULL;
-		if (error)
+		/* xfs_attr3_leaf_create may not have instantiated a block */
+		if (bp && (xfs_da_shrink_inode(args, 0, bp) != 0))
 			goto out;
 		xfs_idata_realloc(dp, size, XFS_ATTR_FORK);	/* try to put */
 		memcpy(ifp->if_u1.if_data, tmpbuffer, size);	/* it back */