ubi: Check whether the Fastmap anchor matches the super block

This helps to detect cases where an user copies an UBI image to
another target with different bad blocks.

Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index 12bdb09..b66cb3e 100644 (file)
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -975,6 +975,13 @@ int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
                        goto free_hdr;
                }
 
+               if (i == 0 && pnum != fm_anchor) {
+                       ubi_err(ubi, "Fastmap anchor PEB mismatch: PEB: %i vs. %i",
+                               pnum, fm_anchor);
+                       ret = UBI_BAD_FASTMAP;
+                       goto free_hdr;
+               }
+
                ret = ubi_io_read_ec_hdr(ubi, pnum, ech, 0);
                if (ret && ret != UBI_IO_BITFLIPS) {
                        ubi_err(ubi, "unable to read fastmap block# %i EC (PEB: %i)",