On Fri, 26 Aug 2016 17:07:08 +0200
Greg Kurz <gr...@kaod.org> wrote:
> According to the 9P spec at http://man.cat-v.org/plan_9/5/intro :
>
> Data items of larger or variable lengths are represented by a
> two-byte field specifying a count, n, followed by n bytes of
> data. Text strings are represented this way, with the text
> itself stored as a UTF-8 encoded sequence of Unicode charac-
> ters (see utf(6)). Text strings in 9P messages are not NUL-
> terminated: n counts the bytes of UTF-8 data, which include
> no final zero byte. The NUL character is illegal in all
> text strings in 9P, and is therefore excluded from file
> names, user names, and so on.
>
> With this patch, if a 9P client sends a text string containing a NUL
> character, the request will fail and the client is returned EINVAL.
>
> The checking is done in v9fs_iov_vunmarshal() because it is a convenient
> place to check all client originated strings.
>
> Suggested-by: Peter Maydell <peter.mayd...@linaro.org>
> Signed-off-by: Greg Kurz <gr...@kaod.org>
> ---
> fsdev/9p-iov-marshal.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c
> index 663cad542900..9bcdc370231d 100644
> --- a/fsdev/9p-iov-marshal.c
> +++ b/fsdev/9p-iov-marshal.c
> @@ -127,7 +127,12 @@ ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int
> out_num, size_t offset,
> str->size);
> if (copied > 0) {
> str->data[str->size] = 0;
> - } else {
> + /* 9P forbids NUL characters in all text strings */
> + if (strlen(str->data) != str->size) {
> + copied = -EINVAL;
> + }
Ugh ! QEMU sends terminating NULs :-\ which cause virtfs-proxy-helper to fail
here during init.
> + }
> + if (copied <= 0) {
> v9fs_string_free(str);
> }
> }
>
>
