[PATCH] ubifs: Check link count of inodes when killing orphans.

[Richard Weinberger]

O_TMPFILE files can change their link count back to non-zero.
This corner case needs to get addressed in the orphans subsystem
too.

Fixes: 474b93704f32 ("ubifs: Implement O_TMPFILE")
Reported-by: Lars Persson <li...@bofh.nu>
Signed-off-by: Richard Weinberger <rich...@nod.at>
---
 fs/ubifs/orphan.c | 39 ++++++++++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index 2f1618f300fb..575c36dfd751 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -642,6 +642,7 @@ static int do_kill_orphans(struct ubifs_info *c, struct 
ubifs_scan_leb *sleb,
 {
        struct ubifs_scan_node *snod;
        struct ubifs_orph_node *orph;
+       struct ubifs_ino_node *ino = NULL;
        unsigned long long cmt_no;
        ino_t inum;
        int i, n, err, first = 1;
@@ -688,23 +689,40 @@ static int do_kill_orphans(struct ubifs_info *c, struct 
ubifs_scan_leb *sleb,
                if (first)
                        first = 0;
 
+               ino = kmalloc(UBIFS_MAX_INO_NODE_SZ, GFP_NOFS);
+               if (!ino)
+                       return -ENOMEM;
+
                n = (le32_to_cpu(orph->ch.len) - UBIFS_ORPH_NODE_SZ) >> 3;
                for (i = 0; i < n; i++) {
                        union ubifs_key key1, key2;
 
                        inum = le64_to_cpu(orph->inos[i]);
-                       dbg_rcvry("deleting orphaned inode %lu",
-                                 (unsigned long)inum);
 
-                       lowest_ino_key(c, &key1, inum);
-                       highest_ino_key(c, &key2, inum);
-
-                       err = ubifs_tnc_remove_range(c, &key1, &key2);
+                       ino_key_init(c, &key1, inum);
+                       err = ubifs_tnc_lookup(c, &key1, ino);
                        if (err)
-                               return err;
+                               goto out_free;
+
+                       /*
+                        * Check whether an inode can really get deleted.
+                        * linkat() with O_TMPFILE allows rebirth of an inode.
+                        */
+                       if (ino->nlink == 0) {
+                               dbg_rcvry("deleting orphaned inode %lu",
+                                         (unsigned long)inum);
+
+                               lowest_ino_key(c, &key1, inum);
+                               highest_ino_key(c, &key2, inum);
+
+                               err = ubifs_tnc_remove_range(c, &key1, &key2);
+                               if (err)
+                                       goto out_err;
+                       }
+
                        err = insert_dead_orphan(c, inum);
                        if (err)
-                               return err;
+                               goto out_err;
                }
 
                *last_cmt_no = cmt_no;
@@ -716,7 +734,10 @@ static int do_kill_orphans(struct ubifs_info *c, struct 
ubifs_scan_leb *sleb,
                        *last_flagged = 0;
        }
 
-       return 0;
+       err = 0;
+out_free:
+       kfree(ino);
+       return err;
 }
 
 /**
-- 
2.16.4