fs/btrfs: Validate the number of stripes/parities in RAID5/6

This prevents a divide by zero if nstripes == nparities, and
also prevents propagation of invalid values if nstripes ends up
less than nparities.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 27339bdb351c420b6aea3f5e15a1bed7bc4ccf92..c4ba5f110dde97fb830b8031920c84db8c119b4b 100644 (file)
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -1083,6 +1083,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
               * stripen is computed without the parities
               * (0 for A0, A1, A2, 1 for B0, B1, B2, etc.).
               */
+             if (nparities >= nstripes)
+               return grub_error (GRUB_ERR_BAD_FS,
+                                  "invalid RAID5/6: nparities >= nstripes");
              high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
 
              /*