fs/adfs: map: fix map scanning

When scanning the map for a fragment id, we need to keep track of the free space links, so we don't inadvertently believe that the freespace link is a valid fragment id. Signed-off-by: Russell King <[email protected]> Signed-off-by: Al Viro <[email protected]>
fracktal · Jan 21, 2020 · f93793f · f93793f
1 parent f6f14a0
commit f93793f
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/fs/adfs/map.c b/fs/adfs/map.c
@@ -72,17 +72,22 @@ static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
 	const u32 idmask = (1 << idlen) - 1;
 	unsigned char *map = dm->dm_bh->b_data;
 	unsigned int start = dm->dm_startbit;
-	unsigned int fragend;
+	unsigned int freelink, fragend;
 	u32 frag;
 
+	frag = GET_FRAG_ID(map, 8, idmask & 0x7fff);
+	freelink = frag ? 8 + frag : 0;
+
 	do {
 		frag = GET_FRAG_ID(map, start, idmask);
 
 		fragend = find_next_bit_le(map, endbit, start + idlen);
 		if (fragend >= endbit)
 			goto error;
 
-		if (frag == frag_id) {
+		if (start == freelink) {
+			freelink += frag & 0x7fff;
+		} else if (frag == frag_id) {
 			unsigned int length = fragend + 1 - start;
 
 			if (*offset < length)