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 9c9eafd6bd7659f79a5ed59a64c0c452448a14cd..70266a3355dc320ef141c4c2b225b5a3e9211003 100644 (file)
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -379,6 +379,8 @@ 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);
@@ -401,6 +403,7 @@ 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 95341bc2b3b7976d110fc1a8551260c247f39269..e38340b218a073db1873a91f3085b35a6ab7bc99 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -91,6 +91,8 @@ 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)) {
@@ -108,6 +110,7 @@ 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;
 }