4.4-stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
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
--- fs/ext4/balloc.c | 3 +++ fs/ext4/ialloc.c | 3 +++ 2 files changed, 6 insertions(+)
--- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -378,6 +378,8 @@ static int ext4_validate_block_bitmap(st 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); @@ -400,6 +402,7 @@ static int ext4_validate_block_bitmap(st return -EFSCORRUPTED; } set_buffer_verified(bh); +verified: ext4_unlock_group(sb, block_group); return 0; } --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -88,6 +88,8 @@ static int ext4_validate_inode_bitmap(st 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)) { @@ -105,6 +107,7 @@ static int ext4_validate_inode_bitmap(st return -EFSBADCRC; } set_buffer_verified(bh); +verified: ext4_unlock_group(sb, block_group); return 0; }