libcontainer:clean cached rlimit nofile in go runtime

As reported in issue opencontainers#4195, the new version of go runtime will cache rlimit-nofile. before executing exec, the rlimit-nofile of the process will be restored with the cache. in runc, this will cause the rlimit-nofile set by the parent process for the container to become invalid. this can be solved by clearing the cache. Signed-off-by: ls-ggg <[email protected]> (cherry picked from commit f9f8abf) Signed-off-by: lifubang <[email protected]>
lifubang · May 5, 2024 · f820328 · f820328
1 parent 163100f
commit f820328
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Showing 4 changed files with 42 additions and 5 deletions.
diff --git a/libcontainer/init_linux.go b/libcontainer/init_linux.go
@@ -649,6 +649,15 @@ func setupRoute(config *configs.Config) error {
 	return nil
 }
 
+func containsRlimit(limits []configs.Rlimit, resource int) bool {
+	for _, rlimit := range limits {
+		if rlimit.Type == resource {
+			return true
+		}
+	}
+	return false
+}
+
 func setupRlimits(limits []configs.Rlimit, pid int) error {
 	for _, rlimit := range limits {
 		if err := unix.Prlimit(pid, rlimit.Type, &unix.Rlimit{Max: rlimit.Hard, Cur: rlimit.Soft}, nil); err != nil {

diff --git a/libcontainer/setns_init_linux.go b/libcontainer/setns_init_linux.go
@@ -49,6 +49,13 @@ func (l *linuxSetnsInit) Init() error {
 			}
 		}
 	}
+
+	// Set RLIMIT_NOFILE again to clean the cache in go runtime
+	// The problem originates from https://github.com/golang/go/commit/f5eef58e4381259cbd84b3f2074c79607fb5c821
+	if containsRlimit(l.config.Rlimits, unix.RLIMIT_NOFILE) {
+		system.ClearRlimitNofileCache()
+	}
+
 	if l.config.CreateConsole {
 		if err := setupConsole(l.consoleSocket, l.config, false); err != nil {
 			return err

diff --git a/libcontainer/standard_init_linux.go b/libcontainer/standard_init_linux.go
@@ -6,17 +6,16 @@ import (
 	"os"
 	"os/exec"
 
-	"github.com/opencontainers/runtime-spec/specs-go"
-	"github.com/opencontainers/selinux/go-selinux"
-	"github.com/sirupsen/logrus"
-	"golang.org/x/sys/unix"
-
 	"github.com/opencontainers/runc/libcontainer/apparmor"
 	"github.com/opencontainers/runc/libcontainer/configs"
 	"github.com/opencontainers/runc/libcontainer/keys"
 	"github.com/opencontainers/runc/libcontainer/seccomp"
 	"github.com/opencontainers/runc/libcontainer/system"
 	"github.com/opencontainers/runc/libcontainer/utils"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/selinux/go-selinux"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
 )
 
 type linuxStandardInit struct {
@@ -77,6 +76,12 @@ func (l *linuxStandardInit) Init() error {
 		}
 	}
 
+	// Set RLIMIT_NOFILE again to clean the cache in go runtime
+	// The problem originates from https://github.com/golang/go/commit/f5eef58e4381259cbd84b3f2074c79607fb5c821
+	if containsRlimit(l.config.Rlimits, unix.RLIMIT_NOFILE) {
+		system.ClearRlimitNofileCache()
+	}
+
 	if err := setupNetwork(l.config); err != nil {
 		return err
 	}

diff --git a/libcontainer/system/linux.go b/libcontainer/system/linux.go
@@ -9,13 +9,29 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
+	"sync/atomic"
 	"syscall"
 	"unsafe"
 
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sys/unix"
 )
 
+//go:linkname syscall_origRlimitNofile syscall.origRlimitNofile
+
+// As reported in issue #4195, the new version of go runtime will
+// cache rlimit-nofile. before executing exec, the rlimit-nofile
+// of the process will be restored with the cache. in runc, this will
+// cause the rlimit-nofile set by the parent process for the container
+// to become invalid. this can be solved by clearing the cache. But
+// unfortunatelly, gostdlib doesn't privede such method, so we need to
+// link to the private var origRlimitNofile in package syscall
+var syscall_origRlimitNofile atomic.Pointer[syscall.Rlimit]
+
+func ClearRlimitNofileCache() {
+	syscall_origRlimitNofile.Store(nil)
+}
+
 type ParentDeathSignal int
 
 func (p ParentDeathSignal) Restore() error {