From dcc2fb3707919c5184480d8cbde98d16f24a3945 Mon Sep 17 00:00:00 2001
From: Michael Reifenberger <mr@FreeBSD.org>
Date: Wed, 21 Apr 2021 20:09:21 +0200
Subject: [PATCH] systat: Avoid incorrect reallocation in pigs.c

Stop free() even if kvm_getprocs as we can come back but set nprocs = 0.
Check nprocs in showpigs() to ensure not try displaying with kvm_getprocs failed.
Current code can have pt with non-null after kvm_getprocs() failure.

Replace to realloc for simpler operations.

Submitted by:	Yoshihiro Ota ota@j.email.ne.jp
Reviewed by:	mckusick@
Differential Revision:	https://reviews.freebsd.org/D29303
---
 usr.bin/systat/pigs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/usr.bin/systat/pigs.c b/usr.bin/systat/pigs.c
index d9f3f8d4ad14..0bec6aceaaa1 100644
--- a/usr.bin/systat/pigs.c
+++ b/usr.bin/systat/pigs.c
@@ -62,7 +62,7 @@ static int nproc;
 static struct p_times {
 	float pt_pctcpu;
 	struct kinfo_proc *pt_kp;
-} *pt;
+} *pt = NULL;
 
 static int    fscale;
 static double  lccpu;
@@ -90,7 +90,7 @@ showpigs(void)
 	const char *uname, *pname;
 	char pidname[30];
 
-	if (pt == NULL)
+	if (nproc == 0)
 		return;
 
 	qsort(pt, nproc, sizeof (struct p_times), compar);
@@ -146,23 +146,20 @@ fetchpigs(void)
 	float ftime;
 	float *pctp;
 	struct kinfo_proc *kpp;
-	static int lastnproc = 0;
+	static int maxnproc = 0;
 
 	if ((kpp = kvm_getprocs(kd, KERN_PROC_ALL, 0, &nproc)) == NULL) {
 		error("%s", kvm_geterr(kd));
-		if (pt)
-			free(pt);
+		nproc = 0;
 		return;
 	}
-	if (nproc > lastnproc) {
-		free(pt);
-		if ((pt =
-		    malloc(nproc * sizeof(struct p_times))) == NULL) {
+	if (nproc > maxnproc) {
+		if ((pt = realloc(pt, nproc * sizeof(*pt))) == NULL) {
 			error("Out of memory");
 			die(0);
 		}
+		maxnproc = nproc;
 	}
-	lastnproc = nproc;
 	/*
 	 * calculate %cpu for each proc
 	 */