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

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>
Cc: stable@vger.kernel.org # 3.7+

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index c3ed9021b781c57cce5d6cff163c216be6c20020..035cd3f4785e2d824be923cbed2c5012b18abb9c 100644 (file)
--- 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 */
                }