Patch "ext4: fix overflow caused by missing cast in ext4_resize_fs()" has been added to the 4.12-stable tree

Patch "ext4: fix overflow caused by missing cast in ext4_resize_fs()" has been added to the 4.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ext4: fix overflow caused by missing cast in ext4_resize_fs()

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-fix-overflow-caused-by-missing-cast-in-ext4_resize_fs.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From aec51758ce10a9c847a62a48a168f8c804c6e053 Mon Sep 17 00:00:00 2001
From: Jerry Lee <jerrylee@qnap.com>
Date: Sun, 6 Aug 2017 01:18:31 -0400
Subject: ext4: fix overflow caused by missing cast in ext4_resize_fs()

From: Jerry Lee <jerrylee@qnap.com>

commit aec51758ce10a9c847a62a48a168f8c804c6e053 upstream.

On a 32-bit platform, the value of n_blcoks_count may be wrong during
the file system is resized to size larger than 2^32 blocks.  This may
caused the superblock being corrupted with zero blocks count.

Fixes: 1c6bd7173d66
Signed-off-by: Jerry Lee <jerrylee@qnap.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/resize.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1927,7 +1927,8 @@ retry:
 			n_desc_blocks = o_desc_blocks +
 				le16_to_cpu(es->s_reserved_gdt_blocks);
 			n_group = n_desc_blocks * EXT4_DESC_PER_BLOCK(sb);
-			n_blocks_count = n_group * EXT4_BLOCKS_PER_GROUP(sb);
+			n_blocks_count = (ext4_fsblk_t)n_group *
+				EXT4_BLOCKS_PER_GROUP(sb);
 			n_group--; /* set to last group number */
 		}
 


Patches currently in stable-queue which might be from jerrylee@qnap.com are

queue-4.12/ext4-fix-overflow-caused-by-missing-cast-in-ext4_resize_fs.patch