From 4097c8d7a8596ddbc9a9db7b7f39c5cbdb1bd742 Mon Sep 17 00:00:00 2001
From: Aleksandr Nogikh <nogikh@google.com>
Date: Wed, 6 Mar 2024 14:47:02 +0100
Subject: sys/linux: clone args before mutation

Not cloning the argument results in replaceArg() replacing a union
argument with itself, which may lead to inconsistent resource
references.

Add an assertion to detect such cases in the future.
---
 prog/clone.go              | 4 ++++
 prog/prog.go               | 3 +++
 sys/linux/init_iptables.go | 4 ++--
 sys/linux/init_vusb.go     | 4 ++--
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/prog/clone.go b/prog/clone.go
index 029cf94c4..4523be0eb 100644
--- a/prog/clone.go
+++ b/prog/clone.go
@@ -39,6 +39,10 @@ func cloneCall(c *Call, newargs map[*ResultArg]*ResultArg) *Call {
 	return c1
 }
 
+func CloneArg(arg Arg) Arg {
+	return clone(arg, nil)
+}
+
 func clone(arg Arg, newargs map[*ResultArg]*ResultArg) Arg {
 	var arg1 Arg
 	switch a := arg.(type) {
diff --git a/prog/prog.go b/prog/prog.go
index f93293b64..da6f158bc 100644
--- a/prog/prog.go
+++ b/prog/prog.go
@@ -354,6 +354,9 @@ func (p *Prog) insertBefore(c *Call, calls []*Call) {
 
 // replaceArg replaces arg with arg1 in a program.
 func replaceArg(arg, arg1 Arg) {
+	if arg == arg1 {
+		panic("replacing an argument with itself")
+	}
 	switch a := arg.(type) {
 	case *ConstArg:
 		*a = *arg1.(*ConstArg)
diff --git a/sys/linux/init_iptables.go b/sys/linux/init_iptables.go
index 7e96662fb..95825d33c 100644
--- a/sys/linux/init_iptables.go
+++ b/sys/linux/init_iptables.go
@@ -31,7 +31,7 @@ func (arch *arch) generateNetfilterTable(g *prog.Gen, typ prog.Type, dir prog.Di
 	} else {
 		// TODO(dvyukov): try to restore original hook order after mutation
 		// instead of assigning brand new offsets.
-		arg = old
+		arg = prog.CloneArg(old)
 		calls = g.MutateArg(arg)
 	}
 	var tableArg *prog.GroupArg
@@ -113,7 +113,7 @@ func (arch *arch) generateEbtables(g *prog.Gen, typ prog.Type, dir prog.Dir, old
 	} else {
 		// TODO(dvyukov): try to restore original hook order after mutation
 		// instead of assigning brand new offsets.
-		arg = old
+		arg = prog.CloneArg(old)
 		calls = g.MutateArg(arg)
 	}
 	if g.Target().ArgContainsAny(arg) {
diff --git a/sys/linux/init_vusb.go b/sys/linux/init_vusb.go
index 5e4244f6e..ca645bf45 100644
--- a/sys/linux/init_vusb.go
+++ b/sys/linux/init_vusb.go
@@ -55,7 +55,7 @@ func (arch *arch) generateUsbDeviceDescriptor(g *prog.Gen, typ0 prog.Type, dir p
 	if old == nil {
 		arg = g.GenerateSpecialArg(typ0, dir, &calls)
 	} else {
-		arg = old
+		arg = prog.CloneArg(old)
 		calls = g.MutateArg(arg)
 	}
 	if g.Target().ArgContainsAny(arg) {
@@ -144,7 +144,7 @@ func (arch *arch) generateUsbHidDeviceDescriptor(g *prog.Gen, typ0 prog.Type, di
 	if old == nil {
 		arg = g.GenerateSpecialArg(typ0, dir, &calls)
 	} else {
-		arg = old
+		arg = prog.CloneArg(old)
 		calls = g.MutateArg(arg)
 	}
 	if g.Target().ArgContainsAny(arg) {
-- 
cgit mrf-deployment