UBIFS: fix double free of ubifs_orphan objects

The last orphan in the dnext list has its dnext set to NULL. Because
of that, ubifs_delete_orphan assumes that it is not on the dnext list
and frees it immediately instead ignoring it as a second delete. The
orphan is later freed again by erase_deleted.

This change adds an explicit flag to ubifs_orphan indicating whether
it is pending delete.

Signed-off-by: Adam Thomas <adamthomas1111@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: stable@vger.kernel.org

2 files changed, 6 insertions, 1 deletions

diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index 8534d9c6492f..ba32da3fe08a 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -126,13 +126,14 @@ void ubifs_delete_orphan(struct ubifs_info *c, ino_t inum)
                 else if (inum > o->inum)
                         p = p->rb_right;
                 else {
-                        if (o->dnext) {
+                        if (o->del) {
                                 spin_unlock(&c->orphan_lock);
                                 dbg_gen("deleted twice ino %lu",
                                         (unsigned long)inum);
                                 return;
                         }
                         if (o->cmt) {
+                                o->del = 1;
                                 o->dnext = c->orph_dnext;
                                 c->orph_dnext = o;
                                 spin_unlock(&c->orphan_lock);
@@ -447,6 +448,7 @@ static void erase_deleted(struct ubifs_info *c)
                 orphan = dnext;
                 dnext = orphan->dnext;
                 ubifs_assert(!orphan->new);
+                ubifs_assert(orphan->del);
                 rb_erase(&orphan->rb, &c->orph_tree);
                 list_del(&orphan->list);
                 c->tot_orphans -= 1;
@@ -536,6 +538,7 @@ static int insert_dead_orphan(struct ubifs_info *c, ino_t inum)
         rb_link_node(&orphan->rb, parent, p);
         rb_insert_color(&orphan->rb, &c->orph_tree);
         list_add_tail(&orphan->list, &c->orph_list);
+        orphan->del = 1;
         orphan->dnext = c->orph_dnext;
         c->orph_dnext = orphan;
         dbg_mnt("ino %lu, new %d, tot %d", (unsigned long)inum,
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index c16fff7271d3..b2babce4d70f 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -905,6 +905,7 @@ struct ubifs_budget_req {
  * @inum: inode number
  * @new: %1 => added since the last commit, otherwise %0
  * @cmt: %1 => commit pending, otherwise %0
+ * @del: %1 => delete pending, otherwise %0
  */
 struct ubifs_orphan {
         struct rb_node rb;
@@ -915,6 +916,7 @@ struct ubifs_orphan {
         ino_t inum;
         unsigned new:1;
         unsigned cmt:1;
+        unsigned del:1;
 };
 
 /**