Re: [PATCH] SUNRPC: fix ternary sign expansion bug in tracing

[Chuck Lever III <chuck.lever@oracle.com>]

> On Apr 22, 2021, at 5:14 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 
> This code is supposed to pass negative "err" values for tracing but it
> passes positive values instead.  The problem is that the
> trace_svcsock_tcp_send() function takes a long but "err" is an int and
> "sent" is a u32.  The negative is first type promoted to u32 so it
> becomes a high positive then it is promoted to long and it stays
> positive.
> 
> Fix this by casting "err" directly to long.
> 
> Fixes: 998024dee197 ("SUNRPC: Add more svcsock tracepoints")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

I had a patch somewhere that simplified this logic and got rid
of the ternary, but I think it got postponed when Trond recently
changed the use of MSG_MORE.

Let's go with this for now. I've pushed it to the for-next
branch at:

git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git


> ---
> net/sunrpc/svcsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 9eb5b6b89077..478f857cdaed 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1174,7 +1174,7 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
> 	tcp_sock_set_cork(svsk->sk_sk, true);
> 	err = svc_tcp_sendmsg(svsk->sk_sock, xdr, marker, &sent);
> 	xdr_free_bvec(xdr);
> -	trace_svcsock_tcp_send(xprt, err < 0 ? err : sent);
> +	trace_svcsock_tcp_send(xprt, err < 0 ? (long)err : sent);
> 	if (err < 0 || sent != (xdr->len + sizeof(marker)))
> 		goto out_close;
> 	if (atomic_dec_and_test(&svsk->sk_sendqlen))
> -- 
> 2.30.2
> 

--
Chuck Lever