Re: [PATCH] tcp_vu: Fix assert/error-check order in tcp_vu_sock_recv()

[Stefano Brivio <sbrivio@redhat.com>]

[Cc: Johannes, Laurent]

Thanks for the patch and the explanation, but shouldn't this be:

On Mon,  9 Nov 2026 17:13:42 -0500
Jon Maloy <jmaloy@redhat.com> wrote:

From: Johannes Bartunek <contact@jbartunek.de>

and:

> iov_tail_clone() returns a ssize_t. However, the assert comparing
> it against (ARRAY_SIZE(iov_msg) - j), which yields size_t, comes
> before the negative-value check. Hence, when iov_tail_clone() fails
> and returns -1, the signed-to-unsigned promotion turns -1 into
> SIZE_MAX, and causes the assert to fire.
> 
> We fix this by moving the error check before the assert, while casting
> the counter and the index inside the assert to size_t.

Reported-by: Johannes Bartunek <contact@jbartunek.de>
Suggested-by: Laurent Vivier <lvivier@redhat.com>

?

> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
>  tcp_vu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tcp_vu.c b/tcp_vu.c
> index 868a35b9..c052d8e2 100644
> --- a/tcp_vu.c
> +++ b/tcp_vu.c
> @@ -291,9 +291,9 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq,
>  
>  		cnt = iov_tail_clone(&iov_msg[j], ARRAY_SIZE(iov_msg) - j,
>  				     &data);
> -		assert(cnt < ARRAY_SIZE(iov_msg) - j);
>  		if (cnt < 0)
>  			die("Missing entries in iov_msg");
> +		assert((size_t)cnt < ARRAY_SIZE(iov_msg) - (size_t)j);
>  
>  		j += cnt;
>  	}

-- 
Stefano