From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 16 Apr 2018 21:35:43 +0000 (-0400)
Subject: fix return value of nice function
X-Git-Tag: v1.1.20~124
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=4bf0717e5141518c1d34ac84253d3973be1fa260;p=oweals%2Fmusl.git

fix return value of nice function

the Linux SYS_nice syscall is unusable because it does not return the
newly set priority. always use SYS_setpriority. also avoid overflows
in addition of inc by handling large inc values directly without
examining the old nice value.
---

diff --git a/src/unistd/nice.c b/src/unistd/nice.c
index da569967..6c25c8c3 100644
--- a/src/unistd/nice.c
+++ b/src/unistd/nice.c
@@ -1,12 +1,16 @@
 #include <unistd.h>
 #include <sys/resource.h>
+#include <limits.h>
 #include "syscall.h"
 
 int nice(int inc)
 {
-#ifdef SYS_nice
-	return syscall(SYS_nice, inc);
-#else
-	return setpriority(PRIO_PROCESS, 0, getpriority(PRIO_PROCESS, 0)+inc);
-#endif
+	int prio = inc;
+	// Only query old priority if it can affect the result.
+	// This also avoids issues with integer overflow.
+	if (inc > -2*NZERO && inc < 2*NZERO)
+		prio += getpriority(PRIO_PROCESS, 0);
+	if (prio > NZERO-1) prio = NZERO-1;
+	if (prio < -NZERO) prio = -NZERO;
+	return setpriority(PRIO_PROCESS, 0, prio) ? -1 : prio;
 }