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

[Alex ThreeD]

Hi all,

Is there something on my side needed to push this forward?

On Wed, Jun 19, 2024 at 12:41 AM Alex Shumsky <alexthreed at gmail.com> wrote:

> 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()")
> ---
>
> 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;
>  }
> --
> 2.34.1
>
>