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authorRich Felker <dalias@aerifal.cx>2018-04-16 17:35:43 -0400
committerRich Felker <dalias@aerifal.cx>2018-04-17 19:23:00 -0400
commit4bf0717e5141518c1d34ac84253d3973be1fa260 (patch)
tree3134e9a2e6c812f370d120efcd4f42c49dd7853f
parent424eab2225ff3f8e3ae9f9eec9dacf2f68b71a2f (diff)
downloadmusl-4bf0717e5141518c1d34ac84253d3973be1fa260.tar.gz
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.
-rw-r--r--src/unistd/nice.c14
1 files changed, 9 insertions, 5 deletions
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;
}