sctp: sctp_sock_filter(): avoid list_entry() on possibly empty list

Use list_is_first() to check whether tsp->asoc matches the first
element of ep->asocs, as the list is not guaranteed to have an entry.

Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/20230208-sctp-filter-v2-1-6e1f4017f326@diag.uniroma1.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sctp/diag.c b/net/sctp/diag.c
index a557009..c3d6b92 100644 (file)
--- a/net/sctp/diag.c
+++ b/net/sctp/diag.c
@@ -343,11 +343,9 @@ static int sctp_sock_filter(struct sctp_endpoint *ep, struct sctp_transport *tsp
        struct sctp_comm_param *commp = p;
        struct sock *sk = ep->base.sk;
        const struct inet_diag_req_v2 *r = commp->r;
-       struct sctp_association *assoc =
-               list_entry(ep->asocs.next, struct sctp_association, asocs);
 
        /* find the ep only once through the transports by this condition */
-       if (tsp->asoc != assoc)
+       if (!list_is_first(&tsp->asoc->asocs, &ep->asocs))
                return 0;
 
        if (r->sdiag_family != AF_UNSPEC && sk->sk_family != r->sdiag_family)