ext4: check for allocation block validity with block group locked

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

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index e68cefe082612c84b39c612ef3ff32fca8ac3d25..aa52d87985aaf30901a52ac6a605357ac6cbea12 100644 (file)
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -368,6 +368,8 @@ 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);
@@ -386,6 +388,7 @@ 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 fb83750c1a14662a2e6337133c2ddb8460956aaf..e9d8e2667ab5b6ddb5628b5da3f18876954166cc 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -90,6 +90,8 @@ 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)) {
@@ -101,6 +103,7 @@ 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;
 }