ext4: don't allow r/w mounts if metadata blocks overlap the superblock

commit 18db4b4e6fc31eda838dd1c1296d67dbcb3dc957 upstream.

If some metadata block, such as an allocation bitmap, overlaps the
superblock, it's very likely that if the file system is mounted
read/write, the results will not be pretty.  So disallow r/w mounts
for file systems corrupted in this particular way.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1339a79eb314e481f3bc4f15b47f246eb2ec895f..3a605c6726490870bc41e3e89ec85baa9caa5308 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2330,6 +2330,8 @@ static int ext4_check_descriptors(struct super_block *sb,
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                                 "Block bitmap for group %u overlaps "
                                 "superblock", i);
+                       if (!sb_rdonly(sb))
+                               return 0;
                }
                if (block_bitmap < first_block || block_bitmap > last_block) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@@ -2342,6 +2344,8 @@ static int ext4_check_descriptors(struct super_block *sb,
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                                 "Inode bitmap for group %u overlaps "
                                 "superblock", i);
+                       if (!sb_rdonly(sb))
+                               return 0;
                }
                if (inode_bitmap < first_block || inode_bitmap > last_block) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@@ -2354,6 +2358,8 @@ static int ext4_check_descriptors(struct super_block *sb,
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                                 "Inode table for group %u overlaps "
                                 "superblock", i);
+                       if (!sb_rdonly(sb))
+                               return 0;
                }
                if (inode_table < first_block ||
                    inode_table + sbi->s_itb_per_group - 1 > last_block) {