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From:   Hou Tao <houtao1@huawei.com>
To:     <linux-mtd@lists.infradead.org>, <dwmw2@infradead.org>
CC:     <linux-kernel@vger.kernel.org>, <richard.weinberger@gmail.com>,
        <boris.brezillon@bootlin.com>
Subject: [PATCH] jffs2: fix invocations of dbg_xattr() for dead jffs2_xattr_ref
Date:   Sat, 20 Oct 2018 19:07:53 +0800
Message-ID: <20181020110753.98407-1-houtao1@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When jffs2_xattr_ref is dead, xref->ic or xref->xd will be invalid
because these fields will be reused as xref->ino or xref->xid,
so access xref->ic->ino or xref->xd->xid will lead to Oops.

Fix the problem by checking whether or not it is a dead xref.

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 fs/jffs2/xattr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 3d40fe02b003..0c4c7891556d 100644
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -550,7 +550,8 @@ static int save_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_ref *ref)
 	ref->xseqno = xseqno;
 	jffs2_add_physical_node_ref(c, phys_ofs | REF_PRISTINE, PAD(sizeof(rr)), (void *)ref);
 
-	dbg_xattr("success on saving xref (ino=%u, xid=%u)\n", ref->ic->ino, ref->xd->xid);
+	dbg_xattr("success on saving xref (ino=%u, xid=%u)\n",
+			je32_to_cpu(rr.ino), je32_to_cpu(rr.xid));
 
 	return 0;
 }
@@ -1329,7 +1330,11 @@ int jffs2_garbage_collect_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_
 	rc = save_xattr_ref(c, ref);
 	if (!rc)
 		dbg_xattr("xref (ino=%u, xid=%u) GC'ed from %#08x to %08x\n",
-			  ref->ic->ino, ref->xd->xid, old_ofs, ref_offset(ref->node));
+				is_xattr_ref_dead(ref) ?
+					ref->ino : ref->ic->ino,
+				is_xattr_ref_dead(ref) ?
+					ref->xid : ref->xd->xid,
+				old_ofs, ref_offset(ref->node));
  out:
 	if (!rc)
 		jffs2_mark_node_obsolete(c, raw);
-- 
2.16.2.dirty