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

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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.

Backport notes:
3.18.y is missing bc98a42c1f7d ("VFS: Convert sb->s_flags & MS_RDONLY to sb_rdonly(sb)")
and e462ec50cb5f ("VFS: Differentiate mount flags (MS_*) from internal superblock flags")
so we simply use the sb MS_RDONLY check from pre bc98a42c1f7d in place of the sb_rdonly
function used in the upstream variant of the patch.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Harsh Shandilya <harsh@prjkt.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Theodore Ts'o 2018-03-29 22:10:35 -04:00 • committed by Greg Kroah-Hartman
parent 7b0278ca9f
commit 4845fefe6d
1 changed files with 6 additions and 0 deletions
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6
fs/ext4/super.c
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@ -2131,6 +2131,8 @@ 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->s_flags & MS_RDONLY))
return 0;
}
if (block_bitmap < first_block || block_bitmap > last_block) {
ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@ -2143,6 +2145,8 @@ 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->s_flags & MS_RDONLY))
return 0;
}
if (inode_bitmap < first_block || inode_bitmap > last_block) {
ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@ -2155,6 +2159,8 @@ 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->s_flags & MS_RDONLY))
return 0;
}
if (inode_table < first_block ||
inode_table + sbi->s_itb_per_group - 1 > last_block) {