UBIFS: fix recovery bug

UBIFS did not recovery in a situation in which it could
have. The relevant function assumed there could not be
more nodes in an eraseblock after a corrupted node, but
in fact the last (NAND) page written might contain anything.
The correct approach is to check for empty space (0xFF bytes)
from then on.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>

1 files changed, 23 insertions, 47 deletions

diff --git a/fs/ubifs/recovery.c b/fs/ubifs/recovery.c
index 90acac603e63..10662975d2ef 100644
--- a/fs/ubifs/recovery.c
+++ b/fs/ubifs/recovery.c
@@ -425,59 +425,35 @@ static void clean_buf(const struct ubifs_info *c, void **buf, int lnum,
  * @lnum: LEB number of the LEB from which @buf was read
  * @offs: offset from which @buf was read
  *
- * This function scans @buf for more nodes and returns %0 is a node is found and
- * %1 if no more nodes are found.
+ * This function ensures that the corrupted node at @offs is the last thing
+ * written to a LEB. This function returns %1 if more data is not found and
+ * %0 if more data is found.
  */
 static int no_more_nodes(const struct ubifs_info *c, void *buf, int len,
                         int lnum, int offs)
 {
-        int skip, next_offs = 0;
+        struct ubifs_ch *ch = buf;
+        int skip, dlen = le32_to_cpu(ch->len);
 
-        if (len > UBIFS_DATA_NODE_SZ) {
-                struct ubifs_ch *ch = buf;
-                int dlen = le32_to_cpu(ch->len);
-
-                if (ch->node_type == UBIFS_DATA_NODE && dlen >= UBIFS_CH_SZ &&
-                    dlen <= UBIFS_MAX_DATA_NODE_SZ)
-                        /* The corrupt node looks like a data node */
-                        next_offs = ALIGN(offs + dlen, 8);
-        }
-
-        if (c->min_io_size == 1)
-                skip = 8;
-        else
-                skip = ALIGN(offs + 1, c->min_io_size) - offs;
-
-        offs += skip;
-        buf += skip;
-        len -= skip;
-        while (len > 8) {
-                struct ubifs_ch *ch = buf;
-                uint32_t magic = le32_to_cpu(ch->magic);
-                int ret;
-
-                if (magic == UBIFS_NODE_MAGIC) {
-                        ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
-                        if (ret == SCANNED_A_NODE || ret > 0) {
-                                /*
-                                 * There is a small chance this is just data in
-                                 * a data node, so check that possibility. e.g.
-                                 * this is part of a file that itself contains
-                                 * a UBIFS image.
-                                 */
-                                if (next_offs && offs + le32_to_cpu(ch->len) <=
-                                    next_offs)
-                                        continue;
-                                dbg_rcvry("unexpected node at %d:%d", lnum,
-                                          offs);
-                                return 0;
-                        }
-                }
-                offs += 8;
-                buf += 8;
-                len -= 8;
+        /* Check for empty space after the corrupt node's common header */
+        skip = ALIGN(offs + UBIFS_CH_SZ, c->min_io_size) - offs;
+        if (is_empty(buf + skip, len - skip))
+                return 1;
+        /*
+         * The area after the common header size is not empty, so the common
+         * header must be intact. Check it.
+         */
+        if (ubifs_check_node(c, buf, lnum, offs, 1, 0) != -EUCLEAN) {
+                dbg_rcvry("unexpected bad common header at %d:%d", lnum, offs);
+                return 0;
         }
-        return 1;
+        /* Now we know the corrupt node's length we can skip over it */
+        skip = ALIGN(offs + dlen, c->min_io_size) - offs;
+        /* After which there should be empty space */
+        if (is_empty(buf + skip, len - skip))
+                return 1;
+        dbg_rcvry("unexpected data at %d:%d", lnum, offs + skip);
+        return 0;
 }
 
 /**