4.9-stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
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 --- fs/ext4/super.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2260,6 +2260,8 @@ static int ext4_check_descriptors(struct 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: " @@ -2272,6 +2274,8 @@ static int ext4_check_descriptors(struct 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: " @@ -2284,6 +2288,8 @@ static int ext4_check_descriptors(struct 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) {