On Tue 21-03-23 09:37:21, Zhihao Cheng wrote:
> Following process makes i_disksize exceed i_size:
>
> generic_perform_write
> copied = iov_iter_copy_from_user_atomic(len) // copied < len
> ext4_da_write_end
> | ext4_update_i_disksize
> | new_i_size = pos + copied;
> | WRITE_ONCE(EXT4_I(inode)->i_disksize, newsize) // update i_disksize
> | generic_write_end
> | copied = block_write_end(copied, len) // copied = 0
> | if (unlikely(copied < len))
> | if (!PageUptodate(page))
> | copied = 0;
> | if (pos + copied > inode->i_size) // return false
> if (unlikely(copied == 0))
> goto again;
> if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
> status = -EFAULT;
> break;
> }
>
> We get i_disksize greater than i_size here, which could trigger WARNING
> check 'i_size_read(inode) < EXT4_I(inode)->i_disksize' while doing dio:
>
> ext4_dio_write_iter
> iomap_dio_rw
> __iomap_dio_rw // return err, length is not aligned to 512
> ext4_handle_inode_extension
> WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize) // Oops
>
> WARNING: CPU: 2 PID: 2609 at fs/ext4/file.c:319
> CPU: 2 PID: 2609 Comm: aa Not tainted 6.3.0-rc2
> RIP: 0010:ext4_file_write_iter+0xbc7
> Call Trace:
> vfs_write+0x3b1
> ksys_write+0x77
> do_syscall_64+0x39
>
> Fix it by updating 'copied' value before updating i_disksize just like
> ext4_write_inline_data_end() does.
>
> Fetch a reproducer in [Link].
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217209
> Fixes: 64769240bd07 ("ext4: Add delayed allocation support in data=writeback mode")
> Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> v1->v2: Check and update 'copied' value before updating i_disksize rather
> than opencoding generic_write_end().
> fs/ext4/inode.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index bf0b7dea4900..41ba1c432844 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3148,6 +3148,9 @@ static int ext4_da_write_end(struct file *file,
> ext4_has_inline_data(inode))
> return ext4_write_inline_data_end(inode, pos, len, copied, page);
>
> + if (unlikely(copied < len) && !PageUptodate(page))
> + copied = 0;
> +
> start = pos & (PAGE_SIZE - 1);
> end = start + copied - 1;
>
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
