[PATCH] xfs_metadump: ignore attr leaf with 0 entries

[Eric Sandeen <sandeen@redhat.com>]

Another in the ongoing saga of attribute leaves with zero
entries; in this case, if we try to metadump an inode with
a zero-entries attribute leaf, the zeroing code will go off
the rails and segfault at:

                memset(&entries[nentries], 0,
                       first_name - (char *)&entries[nentries]);

because first_name is null, and we try to memset a large
(negative) number.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/db/metadump.c b/db/metadump.c
index 38519f1..66952f6 100644
--- a/db/metadump.c
+++ b/db/metadump.c
@@ -1654,7 +1654,8 @@ process_attr_block(
 	xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &hdr, leaf);
 
 	nentries = hdr.count;
-	if (nentries * sizeof(xfs_attr_leaf_entry_t) +
+	if (nentries == 0 ||
+	    nentries * sizeof(xfs_attr_leaf_entry_t) +
 			xfs_attr3_leaf_hdr_size(leaf) >
 				XFS_ATTR3_RMT_BUF_SPACE(mp, bs)) {
 		if (show_warnings)