diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -210,7 +210,7 @@
 static bool	pmc_can_allocate_row(int ri, enum pmc_mode mode);
 static bool	pmc_can_allocate_rowindex(struct proc *p, unsigned int ri,
     int cpu);
-static int	pmc_can_attach(struct pmc *pm, struct proc *p);
+static bool	pmc_can_attach(struct pmc *pm, struct proc *p);
 static void	pmc_capture_user_callchain(int cpu, int soft,
     struct trapframe *tf);
 static void	pmc_cleanup(void);
@@ -1029,19 +1029,19 @@
  * Check if PMC 'pm' may be attached to target process 't'.
  */
 
-static int
+static bool
 pmc_can_attach(struct pmc *pm, struct proc *t)
 {
 	struct proc *o;		/* pmc owner */
 	struct ucred *oc, *tc;	/* owner, target credentials */
-	int decline_attach, i;
+	bool decline_attach;
 
 	/*
 	 * A PMC's owner can always attach that PMC to itself.
 	 */
 
 	if ((o = pm->pm_owner->po_owner) == t)
-		return 0;
+		return (false);
 
 	PROC_LOCK(o);
 	oc = o->p_ucred;
@@ -1066,18 +1066,17 @@
 	 * Every one of the target's group ids, must be in the owner's
 	 * group list.
 	 */
-	for (i = 0; !decline_attach && i < tc->cr_ngroups; i++)
+	for (int i = 0; !decline_attach && i < tc->cr_ngroups; i++)
 		decline_attach = !groupmember(tc->cr_groups[i], oc);
-
-	/* check the read and saved gids too */
-	if (decline_attach == 0)
-		decline_attach = !groupmember(tc->cr_rgid, oc) ||
+	if (!decline_attach)
+		decline_attach = !groupmember(tc->cr_gid, oc) ||
+		    !groupmember(tc->cr_rgid, oc) ||
 		    !groupmember(tc->cr_svgid, oc);
 
 	crfree(tc);
 	crfree(oc);
 
-	return !decline_attach;
+	return (!decline_attach);
 }
 
 /*
@@ -1412,7 +1411,7 @@
 	 */
 	for (ri = 0; ri < md->pmd_npmc; ri++) {
 		if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL) {
-			if (pmc_can_attach(pm, td->td_proc) != 0) {
+			if (pmc_can_attach(pm, td->td_proc)) {
 				pmc_detach_one_process(td->td_proc, pm,
 				    PMC_FLAG_NONE);
 			}