[PATCH v2] fs: btrfs: fix out of bounds write

[Qu Wenruo]

在 2024/6/19 07:11, Alex Shumsky 写道:
> Fix btrfs_read/read_and_truncate_page write out of bounds of destination
> buffer. Old behavior break bootstd malloc'd buffers of exact file size.
> Previously this OOB write have not been noticed because distroboot usually
> read files into huge static memory areas.
>
> Signed-off-by: Alex Shumsky <alexthreed at gmail.com>
> Fixes: e342718 ("fs: btrfs: Implement btrfs_file_read()")

Reviewed-by: Qu Wenruo <wqu at suse.com>

Thanks,
Qu
> ---
>
> Changes in v2:
> - fix error path handling
> - add Fixes tag
> - use min3
>
>   fs/btrfs/inode.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 4691612eda..3998ffc2c8 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -640,7 +640,11 @@ static int read_and_truncate_page(struct btrfs_path *path,
>   	extent_type = btrfs_file_extent_type(leaf, fi);
>   	if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
>   		ret = btrfs_read_extent_inline(path, fi, buf);
> -		memcpy(dest, buf + page_off, min(page_len, ret));
> +		if (ret < 0) {
> +			free(buf);
> +			return ret;
> +		}
> +		memcpy(dest, buf + page_off, min3(page_len, ret, len));
>   		free(buf);
>   		return len;
>   	}
> @@ -652,7 +656,7 @@ static int read_and_truncate_page(struct btrfs_path *path,
>   		free(buf);
>   		return ret;
>   	}
> -	memcpy(dest, buf + page_off, page_len);
> +	memcpy(dest, buf + page_off, min(page_len, len));
>   	free(buf);
>   	return len;
>   }