[PATCH 3.10 071/123] ext4: fix overflow when updating superblock backups after resize

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@xxxxxxx>

commit 9378c6768e4fca48971e7b6a9075bc006eda981d upstream.

When there are no meta block groups update_backups() will compute the
backup block in 32-bit arithmetics thus possibly overflowing the block
number and corrupting the filesystem. OTOH filesystems without meta
block groups larger than 16 TB should be rare. Fix the problem by doing
the counting in 64-bit arithmetics.

Coverity-id: 741252
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1066,7 +1066,7 @@ static void update_backups(struct super_
 			break;
 
 		if (meta_bg == 0)
-			backup_block = group * bpg + blk_off;
+			backup_block = ((ext4_fsblk_t)group) * bpg + blk_off;
 		else
 			backup_block = (ext4_group_first_block_no(sb, group) +
 					ext4_bg_has_super(sb, group));


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/