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ext4: check for allocation block validity with block group locked

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With commit 044e6e3d74: "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
This commit is contained in:
Theodore Ts'o 2018-07-12 19:08:05 -04:00
parent 362eca70b5
commit 8d5a803c6a
2 changed files with 6 additions and 0 deletions
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3
fs/ext4/balloc.c
View file

@ -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;
}

3
fs/ext4/ialloc.c
View file

@ -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;
}