Re: [PATCH v6 1/5] block: Don't invalidate pagecache for invalid falloc modes

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, May 05, 2023 at 11:29:05PM -0700, Sarthak Kukreti wrote:
> Only call truncate_bdev_range() if the fallocate mode is
> supported. This fixes a bug where data in the pagecache
> could be invalidated if the fallocate() was called on the
> block device with an invalid mode.
> 
> Fixes: 25f4c41415e5 ("block: implement (some of) fallocate for block devices")
> Cc: stable@vger.kernel.org
> Reported-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>

Ideally you'd only take filemap_invalidate_lock for valid modes, but eh
who cares about efficiency for the EOPNOTSUPP case, let's move on. :)

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  block/fops.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/block/fops.c b/block/fops.c
> index d2e6be4e3d1c..4c70fdc546e7 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -648,24 +648,35 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
>  
>  	filemap_invalidate_lock(inode->i_mapping);
>  
> -	/* Invalidate the page cache, including dirty pages. */
> -	error = truncate_bdev_range(bdev, file->f_mode, start, end);
> -	if (error)
> -		goto fail;
> -
> +	/*
> +	 * Invalidate the page cache, including dirty pages, for valid
> +	 * de-allocate mode calls to fallocate().
> +	 */
>  	switch (mode) {
>  	case FALLOC_FL_ZERO_RANGE:
>  	case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +		if (error)
> +			goto fail;
> +
>  		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
>  					     len >> SECTOR_SHIFT, GFP_KERNEL,
>  					     BLKDEV_ZERO_NOUNMAP);
>  		break;
>  	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +		if (error)
> +			goto fail;
> +
>  		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
>  					     len >> SECTOR_SHIFT, GFP_KERNEL,
>  					     BLKDEV_ZERO_NOFALLBACK);
>  		break;
>  	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +		if (error)
> +			goto fail;
> +
>  		error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
>  					     len >> SECTOR_SHIFT, GFP_KERNEL);
>  		break;
> -- 
> 2.40.1.521.gf1e218fcd8-goog
>