dont-allow-rw-mounts-of-metadata-blocks-over-lap-sb

   1 ext4: don't allow r/w mounts if metadata blocks overlap the superblock
   2
   3 If some metadata block, such as an allocation bitmap, overlaps the
   4 superblock, it's very likely that if the file system is mounted
   5 read/write, the results will not be pretty.  So disallow r/w mounts
   6 for file systems corrupted in this particular way.
   7
   8 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   9 Cc: stable@vger.kernel.org
  10 ---
  11  fs/ext4/super.c | 6 ++++++
  12  1 file changed, 6 insertions(+)
  13
  14 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  15 index 7cd022c344d1..edcfe6956eba 100644
  16 --- a/fs/ext4/super.c
  17 +++ b/fs/ext4/super.c
  18 @@ -2335,6 +2335,8 @@ static int ext4_check_descriptors(struct super_block *sb,
  19                         ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
  20                                  "Block bitmap for group %u overlaps "
  21                                  "superblock", i);
  22 +                       if (!sb_rdonly(sb))
  23 +                               return 0;
  24                 }
  25                 if (block_bitmap < first_block || block_bitmap > last_block) {
  26                         ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
  27 @@ -2347,6 +2349,8 @@ static int ext4_check_descriptors(struct super_block *sb,
  28                         ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
  29                                  "Inode bitmap for group %u overlaps "
  30                                  "superblock", i);
  31 +                       if (!sb_rdonly(sb))
  32 +                               return 0;
  33                 }
  34                 if (inode_bitmap < first_block || inode_bitmap > last_block) {
  35                         ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
  36 @@ -2359,6 +2363,8 @@ static int ext4_check_descriptors(struct super_block *sb,
  37                         ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
  38                                  "Inode table for group %u overlaps "
  39                                  "superblock", i);
  40 +                       if (!sb_rdonly(sb))
  41 +                               return 0;
  42                 }
  43                 if (inode_table < first_block ||
  44                     inode_table + sbi->s_itb_per_group - 1 > last_block) {