[PATCH v4] xfs_db: release ip resource before returning from get_next_unlinked()

[Bill O'Donnell <bodonnel@redhat.com>]

Fix potential memory leak in function get_next_unlinked(). Call
libxfs_irele(ip) before exiting.

Details:
Error: RESOURCE_LEAK (CWE-772):
xfsprogs-6.5.0/db/iunlink.c:51:2: alloc_arg: "libxfs_iget" allocates memory that is stored into "ip".
xfsprogs-6.5.0/db/iunlink.c:68:2: noescape: Resource "&ip->i_imap" is not freed or pointed-to in "libxfs_imap_to_bp".
xfsprogs-6.5.0/db/iunlink.c:76:2: leaked_storage: Variable "ip" going out of scope leaks the storage it points to.
#   74|   	libxfs_buf_relse(ino_bp);
#   75|
#   76|-> 	return ret;
#   77|   bad:
#   78|   	dbprintf(_("AG %u agino %u: %s\n"), agno, agino, strerror(error));

Signed-off-by: Bill O'Donnell <bodonnel@redhat.com>
---
v2: cover error case.
v3: fix coverage to not release unitialized variable.
v4: add logic to cover error case when ip is not attained.
---
db/iunlink.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/db/iunlink.c b/db/iunlink.c
index d87562e3..98d1effc 100644
--- a/db/iunlink.c
+++ b/db/iunlink.c
@@ -49,8 +49,12 @@ get_next_unlinked(
 
 	ino = XFS_AGINO_TO_INO(mp, agno, agino);
 	error = -libxfs_iget(mp, NULL, ino, 0, &ip);
-	if (error)
-		goto bad;
+	if (error) {
+		if (ip)
+			goto bad_rele;
+		else
+			goto bad;
+	}
 
 	if (verbose) {
 		xfs_filblks_t	blocks, rtblks = 0;
@@ -67,13 +71,16 @@ get_next_unlinked(
 
 	error = -libxfs_imap_to_bp(mp, NULL, &ip->i_imap, &ino_bp);
 	if (error)
-		goto bad;
+		goto bad_rele;
 
 	dip = xfs_buf_offset(ino_bp, ip->i_imap.im_boffset);
 	ret = be32_to_cpu(dip->di_next_unlinked);
 	libxfs_buf_relse(ino_bp);
+	libxfs_irele(ip);
 
 	return ret;
+bad_rele:
+	libxfs_irele(ip);
 bad:
 	dbprintf(_("AG %u agino %u: %s\n"), agno, agino, strerror(error));
 	return NULLAGINO;
-- 
2.46.0