From 41da7a568b1e4f46b3bc09724996556fb18b4d16 Mon Sep 17 00:00:00 2001
From: Ting-Yu Wang <anivia@google.com>
Date: Thu, 4 Jun 2020 15:38:33 -0700
Subject: Fix copylocks error about copying IPTables.

IPTables.connections contains a sync.RWMutex. Copying it will trigger copylocks
analysis. Tested by manually enabling nogo tests.

sync.RWMutex is added to IPTables for the additional race condition discovered.

PiperOrigin-RevId: 314817019
---
 pkg/sentry/socket/netfilter/netfilter.go | 36 +++++++++++++-------------------
 pkg/sentry/socket/netstack/stack.go      |  9 ++++----
 2 files changed, 19 insertions(+), 26 deletions(-)

(limited to 'pkg/sentry')

diff --git a/pkg/sentry/socket/netfilter/netfilter.go b/pkg/sentry/socket/netfilter/netfilter.go
index 47ff48c00..66015e2bc 100644
--- a/pkg/sentry/socket/netfilter/netfilter.go
+++ b/pkg/sentry/socket/netfilter/netfilter.go
@@ -144,31 +144,27 @@ func GetEntries(t *kernel.Task, stack *stack.Stack, outPtr usermem.Addr, outLen
 }
 
 func findTable(stk *stack.Stack, tablename linux.TableName) (stack.Table, error) {
-	ipt := stk.IPTables()
-	table, ok := ipt.Tables[tablename.String()]
+	table, ok := stk.IPTables().GetTable(tablename.String())
 	if !ok {
 		return stack.Table{}, fmt.Errorf("couldn't find table %q", tablename)
 	}
 	return table, nil
 }
 
-// FillDefaultIPTables sets stack's IPTables to the default tables and
-// populates them with metadata.
-func FillDefaultIPTables(stk *stack.Stack) {
-	ipt := stack.DefaultTables()
-
-	// In order to fill in the metadata, we have to translate ipt from its
-	// netstack format to Linux's giant-binary-blob format.
-	for name, table := range ipt.Tables {
-		_, metadata, err := convertNetstackToBinary(name, table)
-		if err != nil {
-			panic(fmt.Errorf("Unable to set default IP tables: %v", err))
+// FillIPTablesMetadata populates stack's IPTables with metadata.
+func FillIPTablesMetadata(stk *stack.Stack) {
+	stk.IPTables().ModifyTables(func(tables map[string]stack.Table) {
+		// In order to fill in the metadata, we have to translate ipt from its
+		// netstack format to Linux's giant-binary-blob format.
+		for name, table := range tables {
+			_, metadata, err := convertNetstackToBinary(name, table)
+			if err != nil {
+				panic(fmt.Errorf("Unable to set default IP tables: %v", err))
+			}
+			table.SetMetadata(metadata)
+			tables[name] = table
 		}
-		table.SetMetadata(metadata)
-		ipt.Tables[name] = table
-	}
-
-	stk.SetIPTables(ipt)
+	})
 }
 
 // convertNetstackToBinary converts the iptables as stored in netstack to the
@@ -573,15 +569,13 @@ func SetEntries(stk *stack.Stack, optVal []byte) *syserr.Error {
 	// - There are no chains without an unconditional final rule.
 	// - There are no chains without an unconditional underflow rule.
 
-	ipt := stk.IPTables()
 	table.SetMetadata(metadata{
 		HookEntry:  replace.HookEntry,
 		Underflow:  replace.Underflow,
 		NumEntries: replace.NumEntries,
 		Size:       replace.Size,
 	})
-	ipt.Tables[replace.Name.String()] = table
-	stk.SetIPTables(ipt)
+	stk.IPTables().ReplaceTable(replace.Name.String(), table)
 
 	return nil
 }
diff --git a/pkg/sentry/socket/netstack/stack.go b/pkg/sentry/socket/netstack/stack.go
index f5fa18136..9b44c2b89 100644
--- a/pkg/sentry/socket/netstack/stack.go
+++ b/pkg/sentry/socket/netstack/stack.go
@@ -362,14 +362,13 @@ func (s *Stack) RouteTable() []inet.Route {
 }
 
 // IPTables returns the stack's iptables.
-func (s *Stack) IPTables() (stack.IPTables, error) {
+func (s *Stack) IPTables() (*stack.IPTables, error) {
 	return s.Stack.IPTables(), nil
 }
 
-// FillDefaultIPTables sets the stack's iptables to the default tables, which
-// allow and do not modify all traffic.
-func (s *Stack) FillDefaultIPTables() {
-	netfilter.FillDefaultIPTables(s.Stack)
+// FillIPTablesMetadata populates stack's IPTables with metadata.
+func (s *Stack) FillIPTablesMetadata() {
+	netfilter.FillIPTablesMetadata(s.Stack)
 }
 
 // Resume implements inet.Stack.Resume.
-- 
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