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 f8b5635f0396ae0d0b276931fb53beddf8b56ab7..e4eab3a38e7c09cd343e84052961cd009c3af913 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 478b8f21c81499b9831f51245571d91712190495..660be3cb363c520455ab60331f3bc06e59d4f3b8 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;
 }