Remove weak references from unix sockets.

The abstract socket namespace no longer holds any references on sockets.
Instead, TryIncRef() is used when a socket is being retrieved in
BoundEndpoint(). Abstract sockets are now responsible for removing themselves
from the namespace they are in, when they are destroyed.

Updates #1486.

PiperOrigin-RevId: 327064173

3 files changed, 36 insertions, 6 deletions

diff --git a/pkg/sentry/socket/unix/BUILD b/pkg/sentry/socket/unix/BUILD
index 061a689a9..cb953e4dc 100644
--- a/pkg/sentry/socket/unix/BUILD
+++ b/pkg/sentry/socket/unix/BUILD
@@ -1,12 +1,25 @@
 load("//tools:defs.bzl", "go_library")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
 
 package(licenses = ["notice"])
 
+go_template_instance(
+    name = "socket_refs",
+    out = "socket_refs.go",
+    package = "unix",
+    prefix = "socketOpsCommon",
+    template = "//pkg/refs_vfs2:refs_template",
+    types = {
+        "T": "socketOpsCommon",
+    },
+)
+
 go_library(
     name = "unix",
     srcs = [
         "device.go",
         "io.go",
+        "socket_refs.go",
         "unix.go",
         "unix_vfs2.go",
     ],
@@ -15,6 +28,7 @@ go_library(
         "//pkg/abi/linux",
         "//pkg/context",
         "//pkg/fspath",
+        "//pkg/log",
         "//pkg/refs",
         "//pkg/safemem",
         "//pkg/sentry/arch",
diff --git a/pkg/sentry/socket/unix/unix.go b/pkg/sentry/socket/unix/unix.go
index 2b8454edb..b7e8e4325 100644
--- a/pkg/sentry/socket/unix/unix.go
+++ b/pkg/sentry/socket/unix/unix.go
@@ -24,7 +24,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
-	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
@@ -80,7 +79,7 @@ func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, sty
 			stype: stype,
 		},
 	}
-	s.EnableLeakCheck("unix.SocketOperations")
+	s.EnableLeakCheck()
 
 	return fs.NewFile(ctx, d, flags, &s)
 }
@@ -89,17 +88,26 @@ func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, sty
 //
 // +stateify savable
 type socketOpsCommon struct {
-	refs.AtomicRefCount
+	socketOpsCommonRefs
 	socket.SendReceiveTimeout
 
 	ep    transport.Endpoint
 	stype linux.SockType
+
+	// abstractName and abstractNamespace indicate the name and namespace of the
+	// socket if it is bound to an abstract socket namespace. Once the socket is
+	// bound, they cannot be modified.
+	abstractName      string
+	abstractNamespace *kernel.AbstractSocketNamespace
 }
 
 // DecRef implements RefCounter.DecRef.
 func (s *socketOpsCommon) DecRef(ctx context.Context) {
-	s.DecRefWithDestructor(ctx, func(context.Context) {
+	s.socketOpsCommonRefs.DecRef(func() {
 		s.ep.Close(ctx)
+		if s.abstractNamespace != nil {
+			s.abstractNamespace.Remove(s.abstractName, s)
+		}
 	})
 }
 
@@ -284,10 +292,14 @@ func (s *SocketOperations) Bind(t *kernel.Task, sockaddr []byte) *syserr.Error {
 			if t.IsNetworkNamespaced() {
 				return syserr.ErrInvalidEndpointState
 			}
-			if err := t.AbstractSockets().Bind(t, p[1:], bep, s); err != nil {
+			asn := t.AbstractSockets()
+			name := p[1:]
+			if err := asn.Bind(t, name, bep, s); err != nil {
 				// syserr.ErrPortInUse corresponds to EADDRINUSE.
 				return syserr.ErrPortInUse
 			}
+			s.abstractName = name
+			s.abstractNamespace = asn
 		} else {
 			// The parent and name.
 			var d *fs.Dirent
diff --git a/pkg/sentry/socket/unix/unix_vfs2.go b/pkg/sentry/socket/unix/unix_vfs2.go
index dfa25241a..d066ef8ab 100644
--- a/pkg/sentry/socket/unix/unix_vfs2.go
+++ b/pkg/sentry/socket/unix/unix_vfs2.go
@@ -183,10 +183,14 @@ func (s *SocketVFS2) Bind(t *kernel.Task, sockaddr []byte) *syserr.Error {
 			if t.IsNetworkNamespaced() {
 				return syserr.ErrInvalidEndpointState
 			}
-			if err := t.AbstractSockets().Bind(t, p[1:], bep, s); err != nil {
+			asn := t.AbstractSockets()
+			name := p[1:]
+			if err := asn.Bind(t, name, bep, s); err != nil {
 				// syserr.ErrPortInUse corresponds to EADDRINUSE.
 				return syserr.ErrPortInUse
 			}
+			s.abstractName = name
+			s.abstractNamespace = asn
 		} else {
 			path := fspath.Parse(p)
 			root := t.FSContext().RootDirectoryVFS2()