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    Subject[PATCH 4.19 32/58] ocfs2: fix data corruption by fallocate
    Date
    From: Junxiao Bi <junxiao.bi@oracle.com>

    commit 6bba4471f0cc1296fe3c2089b9e52442d3074b2e upstream.

    When fallocate punches holes out of inode size, if original isize is in
    the middle of last cluster, then the part from isize to the end of the
    cluster will be zeroed with buffer write, at that time isize is not yet
    updated to match the new size, if writeback is kicked in, it will invoke
    ocfs2_writepage()->block_write_full_page() where the pages out of inode
    size will be dropped. That will cause file corruption. Fix this by
    zero out eof blocks when extending the inode size.

    Running the following command with qemu-image 4.2.1 can get a corrupted
    coverted image file easily.

    qemu-img convert -p -t none -T none -f qcow2 $qcow_image \
    -O qcow2 -o compat=1.1 $qcow_image.conv

    The usage of fallocate in qemu is like this, it first punches holes out
    of inode size, then extend the inode size.

    fallocate(11, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 2276196352, 65536) = 0
    fallocate(11, 0, 2276196352, 65536) = 0

    v1: https://www.spinics.net/lists/linux-fsdevel/msg193999.html
    v2: https://lore.kernel.org/linux-fsdevel/20210525093034.GB4112@quack2.suse.cz/T/

    Link: https://lkml.kernel.org/r/20210528210648.9124-1-junxiao.bi@oracle.com
    Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
    Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
    Cc: Jan Kara <jack@suse.cz>
    Cc: Mark Fasheh <mark@fasheh.com>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Changwei Ge <gechangwei@live.cn>
    Cc: Gang He <ghe@suse.com>
    Cc: Jun Piao <piaojun@huawei.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/ocfs2/file.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
    1 file changed, 50 insertions(+), 5 deletions(-)

    --- a/fs/ocfs2/file.c
    +++ b/fs/ocfs2/file.c
    @@ -1864,6 +1864,45 @@ out:
    }

    /*
    + * zero out partial blocks of one cluster.
    + *
    + * start: file offset where zero starts, will be made upper block aligned.
    + * len: it will be trimmed to the end of current cluster if "start + len"
    + * is bigger than it.
    + */
    +static int ocfs2_zeroout_partial_cluster(struct inode *inode,
    + u64 start, u64 len)
    +{
    + int ret;
    + u64 start_block, end_block, nr_blocks;
    + u64 p_block, offset;
    + u32 cluster, p_cluster, nr_clusters;
    + struct super_block *sb = inode->i_sb;
    + u64 end = ocfs2_align_bytes_to_clusters(sb, start);
    +
    + if (start + len < end)
    + end = start + len;
    +
    + start_block = ocfs2_blocks_for_bytes(sb, start);
    + end_block = ocfs2_blocks_for_bytes(sb, end);
    + nr_blocks = end_block - start_block;
    + if (!nr_blocks)
    + return 0;
    +
    + cluster = ocfs2_bytes_to_clusters(sb, start);
    + ret = ocfs2_get_clusters(inode, cluster, &p_cluster,
    + &nr_clusters, NULL);
    + if (ret)
    + return ret;
    + if (!p_cluster)
    + return 0;
    +
    + offset = start_block - ocfs2_clusters_to_blocks(sb, cluster);
    + p_block = ocfs2_clusters_to_blocks(sb, p_cluster) + offset;
    + return sb_issue_zeroout(sb, p_block, nr_blocks, GFP_NOFS);
    +}
    +
    +/*
    * Parts of this function taken from xfs_change_file_space()
    */
    static int __ocfs2_change_file_space(struct file *file, struct inode *inode,
    @@ -1873,7 +1912,7 @@ static int __ocfs2_change_file_space(str
    {
    int ret;
    s64 llen;
    - loff_t size;
    + loff_t size, orig_isize;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct buffer_head *di_bh = NULL;
    handle_t *handle;
    @@ -1904,6 +1943,7 @@ static int __ocfs2_change_file_space(str
    goto out_inode_unlock;
    }

    + orig_isize = i_size_read(inode);
    switch (sr->l_whence) {
    case 0: /*SEEK_SET*/
    break;
    @@ -1911,7 +1951,7 @@ static int __ocfs2_change_file_space(str
    sr->l_start += f_pos;
    break;
    case 2: /*SEEK_END*/
    - sr->l_start += i_size_read(inode);
    + sr->l_start += orig_isize;
    break;
    default:
    ret = -EINVAL;
    @@ -1965,6 +2005,14 @@ static int __ocfs2_change_file_space(str
    default:
    ret = -EINVAL;
    }
    +
    + /* zeroout eof blocks in the cluster. */
    + if (!ret && change_size && orig_isize < size) {
    + ret = ocfs2_zeroout_partial_cluster(inode, orig_isize,
    + size - orig_isize);
    + if (!ret)
    + i_size_write(inode, size);
    + }
    up_write(&OCFS2_I(inode)->ip_alloc_sem);
    if (ret) {
    mlog_errno(ret);
    @@ -1981,9 +2029,6 @@ static int __ocfs2_change_file_space(str
    goto out_inode_unlock;
    }

    - if (change_size && i_size_read(inode) < size)
    - i_size_write(inode, size);
    -
    inode->i_ctime = inode->i_mtime = current_time(inode);
    ret = ocfs2_mark_inode_dirty(handle, inode, di_bh);
    if (ret < 0)

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