xfs: fix uninitialized variable access

Darrick J. Wong · Darrick J. Wong · commit 60b730a40c43 · 2023-02-14T17:51:35.000-08:00
If the end position of a GETFSMAP query overlaps an allocated space and
we're using the free space info to generate fsmap info, the akeys
information gets fed into the fsmap formatter with bad results.
Zero-init the space.

Reported-by: syzbot+090ae72d552e6bd93cfe@syzkaller.appspotmail.com
Signed-off-by: Darrick J. Wong &lt;djwong@kernel.org&gt;
diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
@@ -761,6 +761,7 @@ xfs_getfsmap_datadev_bnobt(
 {
 	struct xfs_alloc_rec_incore	akeys[2];
 
+	memset(akeys, 0, sizeof(akeys));
 	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
 	return __xfs_getfsmap_datadev(tp, keys, info,
 			xfs_getfsmap_datadev_bnobt_query, &akeys[0]);

Original file line number	Diff line number	Diff line change
`@@ -761,6 +761,7 @@ xfs_getfsmap_datadev_bnobt(`
`761`	`761`	`{`
`762`	`762`	`struct xfs_alloc_rec_incore akeys[2];`
`763`	`763`
	`764`	`+ memset(akeys, 0, sizeof(akeys));`
`764`	`765`	`info->missing_owner = XFS_FMR_OWN_UNKNOWN;`
`765`	`766`	`return __xfs_getfsmap_datadev(tp, keys, info,`
`766`	`767`	`xfs_getfsmap_datadev_bnobt_query, &akeys[0]);`