syscall: don't change local limit if prlimit used for another process

src/syscall/export_linux_test.go

@@ -11,6 +11,7 @@ import (
 var (
  RawSyscallNoError = rawSyscallNoError
  ForceClone3 = &forceClone3
+ Prlimit = prlimit
 )
 
 const (

src/syscall/export_rlimit_test.go

@@ -6,6 +6,12 @@
 
 package syscall
 
+import "sync/atomic"
+
 func OrigRlimitNofile() *Rlimit {
  return origRlimitNofile.Load()
 }
+
+func GetInternalOrigRlimitNofile() *atomic.Pointer[Rlimit] {
+ return &origRlimitNofile
+}

src/syscall/syscall_linux.go

@@ -1289,7 +1289,7 @@ func Munmap(b []byte) (err error) {
 // This is unexported but can be called from x/sys/unix.
 func prlimit(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) {
  err = prlimit1(pid, resource, newlimit, old)
- if err == nil && newlimit != nil && resource == RLIMIT_NOFILE {
+ if err == nil && newlimit != nil && resource == RLIMIT_NOFILE && (pid == 0 || pid == Getpid()) {
  origRlimitNofile.Store(nil)
  }
  return err

src/syscall/syscall_linux_test.go

@@ -654,3 +654,69 @@ func TestAllThreadsSyscallBlockedSyscall(t *testing.T) {
  wr.Close()
  wg.Wait()
 }
+
+func TestPrlimitSelf(t *testing.T) {
+ origLimit := syscall.OrigRlimitNofile()
+ origRlimitNofile := syscall.GetInternalOrigRlimitNofile()
+
+ if origLimit == nil {
+ defer origRlimitNofile.Store(origLimit)
+ origRlimitNofile.Store(&syscall.Rlimit{
+ Cur: 1024,
+ Max: 65536,
+ })
+ }
+
+ // Get current process's nofile limit
+ var lim syscall.Rlimit
+ if err := syscall.Prlimit(0, syscall.RLIMIT_NOFILE, nil, &lim); err != nil {
+ t.Fatalf("Failed to get the current nofile limit: %v", err)
+ }
+ // Set current process's nofile limit through prlimit
+ if err := syscall.Prlimit(0, syscall.RLIMIT_NOFILE, &lim, nil); err != nil {
+ t.Fatalf("Prlimit self failed: %v", err)
+ }
+
+ rlimLater := origRlimitNofile.Load()
+ if rlimLater != nil {
+ t.Fatalf("origRlimitNofile got=%v, want=nil", rlimLater)
+ }
+}
+
+func TestPrlimitOtherProcess(t *testing.T) {
+ origLimit := syscall.OrigRlimitNofile()
+ origRlimitNofile := syscall.GetInternalOrigRlimitNofile()
+
+ if origLimit == nil {
+ defer origRlimitNofile.Store(origLimit)
+ origRlimitNofile.Store(&syscall.Rlimit{
+ Cur: 1024,
+ Max: 65536,
+ })
+ }
+ rlimOrig := origRlimitNofile.Load()
+
+ // Start a child process firstly,
+ // so we can use Prlimit to set it's nofile limit.
+ cmd := exec.Command("sleep", "infinity")
+ cmd.Start()
+ defer func() {
+ cmd.Process.Kill()
+ cmd.Process.Wait()
+ }()
+
+ // Get child process's current nofile limit
+ var lim syscall.Rlimit
+ if err := syscall.Prlimit(cmd.Process.Pid, syscall.RLIMIT_NOFILE, nil, &lim); err != nil {
+ t.Fatalf("Failed to get the current nofile limit: %v", err)
+ }
+ // Set child process's nofile rlimit through prlimit
+ if err := syscall.Prlimit(cmd.Process.Pid, syscall.RLIMIT_NOFILE, &lim, nil); err != nil {
+ t.Fatalf("Prlimit(%d) failed: %v", cmd.Process.Pid, err)
+ }
+
+ rlimLater := origRlimitNofile.Load()
+ if rlimLater != rlimOrig {
+ t.Fatalf("origRlimitNofile got=%v, want=%v", rlimLater, rlimOrig)
+ }
+}