ext4: check for allocation block validity with block group locked

commit 8d5a803c6a6ce4ec258e31f76059ea5153ba46ef upstream.

With commit 044e6e3d74a3: "ext4: don't update checksum of new
initialized bitmaps" the buffer valid bit will get set without
actually setting up the checksum for the allocation bitmap, since the
checksum will get calculated once we actually allocate an inode or
block.

If we are doing this, then we need to (re-)check the verified bit
after we take the block group lock.  Otherwise, we could race with
another process reading and verifying the bitmap, which would then
complain about the checksum being invalid.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1780137

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

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 092da164bdc0b83a91fbeb6eb49cbf8b9d6a5a02..e0fb7cdcee897716b925e5623b98afce34057f90 100644 (file)
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -378,6 +378,8 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
                return -EFSCORRUPTED;
 
        ext4_lock_group(sb, block_group);
+       if (buffer_verified(bh))
+               goto verified;
        if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
                        desc, bh))) {
                ext4_unlock_group(sb, block_group);
@@ -400,6 +402,7 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
                return -EFSCORRUPTED;
        }
        set_buffer_verified(bh);
+verified:
        ext4_unlock_group(sb, block_group);
        return 0;
 }

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 48d818eba9c3388d50c7c945cd1366de608d7e11..041117fd8fd7f1c1b8171e8ded3ac26f106176f7 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -88,6 +88,8 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
                return -EFSCORRUPTED;
 
        ext4_lock_group(sb, block_group);
+       if (buffer_verified(bh))
+               goto verified;
        blk = ext4_inode_bitmap(sb, desc);
        if (!ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
                                           EXT4_INODES_PER_GROUP(sb) / 8)) {
@@ -105,6 +107,7 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
                return -EFSBADCRC;
        }
        set_buffer_verified(bh);
+verified:
        ext4_unlock_group(sb, block_group);
        return 0;
 }