From a005682edd852f7d44903885504d1bfbf313c98a Mon Sep 17 00:00:00 2001
From: Darren Kenny <darren.kenny@oracle.com>
Date: Tue, 8 Dec 2020 22:17:04 +0000
Subject: [PATCH] zfs: Fix possible integer overflows

In all cases the problem is that the value being acted upon by
a left-shift is a 32-bit number which is then being used in the
context of a 64-bit number.

To avoid overflow we ensure that the number being shifted is 64-bit
before the shift is done.

Fixes: CID 73684, CID 73695, CID 73764

Reference: http://git.savannah.gnu.org/cgit/grub.git/commit/?id=302c12ff5714bc455949117c1c9548ccb324d55b

Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/zfs/zfs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/grub-core/fs/zfs/zfs.c b/grub-core/fs/zfs/zfs.c
index 98567a7..e3b5f50 100644
--- a/grub-core/fs/zfs/zfs.c
+++ b/grub-core/fs/zfs/zfs.c
@@ -564,7 +564,7 @@ find_bestub (uberblock_phys_t * ub_array,
       ubptr = (uberblock_phys_t *) ((grub_properly_aligned_t *) ub_array
 				    + ((i << ub_shift)
 				       / sizeof (grub_properly_aligned_t)));
-      err = uberblock_verify (ubptr, offset, 1 << ub_shift);
+      err = uberblock_verify (ubptr, offset, (grub_size_t) 1 << ub_shift);
       if (err)
 	{
 	  grub_errno = GRUB_ERR_NONE;
@@ -1543,7 +1543,7 @@ read_device (grub_uint64_t offset, struct grub_zfs_device_desc *desc,
 
 	    high = grub_divmod64 ((offset >> desc->ashift) + c,
 				  desc->n_children, &devn);
-	    csize = bsize << desc->ashift;
+	    csize = (grub_size_t) bsize << desc->ashift;
 	    if (csize > len)
 	      csize = len;
 
@@ -1635,8 +1635,8 @@ read_device (grub_uint64_t offset, struct grub_zfs_device_desc *desc,
 
 	    while (len > 0)
 	      {
-		grub_size_t csize;
-		csize = ((s / (desc->n_children - desc->nparity))
+		grub_size_t csize = s;
+		csize = ((csize / (desc->n_children - desc->nparity))
 			 << desc->ashift);
 		if (csize > len)
 		  csize = len;
-- 
2.19.1