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: 1c6bd71 Signed-off-by: Jerry Lee <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]> Cc: [email protected] # 3.7+
ambv · Aug 6, 2017 · aec5175 · aec5175
1 parent c03b45b
commit aec5175
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
@@ -1927,7 +1927,8 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 			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 */
 		}