Index: lib/libc/sys/kill.2
===================================================================
--- lib/libc/sys/kill.2
+++ lib/libc/sys/kill.2
@@ -28,7 +28,7 @@
 .\"     @(#)kill.2	8.3 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd December 1, 2017
+.Dd December 1, 2019
 .Dt KILL 2
 .Os
 .Sh NAME
@@ -105,12 +105,11 @@
 .Xr init 8 ) ,
 and the process sending the signal.
 If the user is not the super user, the signal is sent to all processes
-with the same uid as the user excluding the process sending the signal.
+which the caller has permissions to, excluding the process sending the signal.
 No error is returned if any process could be signaled.
 .El
 .Pp
-For compatibility with System V,
-if the process number is negative but not -1,
+If the process number is negative but not -1,
 the signal is sent to all processes whose process group ID
 is equal to the absolute value of the process number.
 This is a variant of
@@ -134,7 +133,7 @@
 .It Bq Er EPERM
 The sending process does not have permission to send
 .Va sig
-to the receiving process.
+to any receiving process.
 .El
 .Sh SEE ALSO
 .Xr getpgrp 2 ,
Index: sys/kern/kern_sig.c
===================================================================
--- sys/kern/kern_sig.c
+++ sys/kern/kern_sig.c
@@ -1688,10 +1688,11 @@
 {
 	struct proc *p;
 	struct pgrp *pgrp;
-	int err;
-	int ret;
+	int err, ret;
+	bool sent, found;
 
-	ret = ESRCH;
+	ret = 0;
+	sent = found = false;
 	if (all) {
 		/*
 		 * broadcast
@@ -1702,15 +1703,16 @@
 			    p == td->td_proc || p->p_state == PRS_NEW) {
 				continue;
 			}
+			found = true;
 			PROC_LOCK(p);
 			err = p_cansignal(td, p, sig);
 			if (err == 0) {
-				if (sig)
+				if (sig != 0)
 					pksignal(p, sig, ksi);
+				sent = true;
+			} else if (ret == 0 && err != ESRCH && err != EPERM) {
 				ret = err;
 			}
-			else if (ret == ESRCH)
-				ret = err;
 			PROC_UNLOCK(p);
 		}
 		sx_sunlock(&allproc_lock);
@@ -1737,18 +1739,22 @@
 				PROC_UNLOCK(p);
 				continue;
 			}
+			found = true;
 			err = p_cansignal(td, p, sig);
 			if (err == 0) {
-				if (sig)
+				if (sig != 0)
 					pksignal(p, sig, ksi);
+				sent = true;
+			} else if (ret == 0 && err != ESRCH && err != EPERM) {
 				ret = err;
 			}
-			else if (ret == ESRCH)
-				ret = err;
 			PROC_UNLOCK(p);
 		}
 		PGRP_UNLOCK(pgrp);
 	}
+	MPASS(ret != 0 || found || !sent);
+	if (ret == 0 && !sent)
+		ret = found ? EPERM : ESRCH;
 	return (ret);
 }