From 356c74f00ed24b08810dc236f37caaca228e5853 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Mon, 18 Jan 2021 17:17:16 +1100
Subject: [PATCH] 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.

Reference: http://git.savannah.gnu.org/cgit/grub.git/commit/?id=b88a82e78cdd0ab8e0339c1c3f9564c4d8c0c969

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 0d8c666..a6384a8 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -1105,6 +1105,9 @@ 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);
 
 	      /*
-- 
2.19.1