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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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Theodore Ts'o 2018-07-12 19:08:05 -04:00 committed by syphyr
parent b2ed801991
commit b3fa07b64d
2 changed files with 7 additions and 1 deletions
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3
fs/ext4/balloc.c
View File

@ -374,6 +374,8 @@ void ext4_validate_block_bitmap(struct super_block *sb,
return;
ext4_lock_group(sb, block_group);
if (buffer_verified(bh))
goto verified;
blk = ext4_valid_block_bitmap(sb, desc, block_group, bh);
if (unlikely(blk != 0)) {
ext4_unlock_group(sb, block_group);
@ -396,6 +398,7 @@ void ext4_validate_block_bitmap(struct super_block *sb,
return;
}
set_buffer_verified(bh);
verified:
ext4_unlock_group(sb, block_group);
}

5
fs/ext4/ialloc.c
View File

@ -167,6 +167,8 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
verify:
ext4_lock_group(sb, block_group);
if (buffer_verified(bh))
goto verified;
if (!buffer_verified(bh) &&
!ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
EXT4_INODES_PER_GROUP(sb) / 8)) {
@ -184,8 +186,9 @@ verify:
set_bit(EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT, &grp->bb_state);
return NULL;
}
ext4_unlock_group(sb, block_group);
set_buffer_verified(bh);
verified:
ext4_unlock_group(sb, block_group);
return bh;
}