csource, executor: add usb emulation feature

The feature gets enabled when /dev/raw-gadget is present and accessible.
With this feature enabled, executor will do chmod 0666 /dev/raw-gadget on
startup, which makes it possible to do USB fuzzing in setuid and namespace
sandboxes. There should be no backwards compatibility issues with syz
reproducers that don't explicitly enable this feature, as they currently only
work in none sandbox.

8 files changed, 44 insertions, 3 deletions

diff --git a/pkg/csource/common.go b/pkg/csource/common.go
index 542cf36bb..96d719b67 100644
--- a/pkg/csource/common.go
+++ b/pkg/csource/common.go
@@ -112,6 +112,7 @@ func commonDefines(p *prog.Prog, opts Options) map[string]bool {
 		"SYZ_CLOSE_FDS":                 opts.CloseFDs,
 		"SYZ_KCSAN":                     opts.KCSAN,
 		"SYZ_DEVLINK_PCI":               opts.DevlinkPCI,
+		"SYZ_USB":                       opts.USB,
 		"SYZ_USE_TMP_DIR":               opts.UseTmpDir,
 		"SYZ_HANDLE_SEGV":               opts.HandleSegv,
 		"SYZ_REPRO":                     opts.Repro,
diff --git a/pkg/csource/generated.go b/pkg/csource/generated.go
index 3bf6c0aa8..98619862b 100644
--- a/pkg/csource/generated.go
+++ b/pkg/csource/generated.go
@@ -7066,6 +7066,14 @@ static void setup_kcsan_filterlist(char** frames, int nframes, bool blacklist)
 #endif
 #endif
 
+#if SYZ_EXECUTOR || SYZ_USB
+static void setup_usb()
+{
+	if (chmod("/dev/raw-gadget", 0666))
+		fail("failed to chmod /dev/raw-gadget");
+}
+#endif
+
 #elif GOOS_test
 
 #include <stdlib.h>
@@ -7549,6 +7557,9 @@ int main(void)
 #if SYZ_KCSAN
 	setup_kcsan();
 #endif
+#if SYZ_USB
+	setup_usb();
+#endif
 
 #if SYZ_HANDLE_SEGV
 	install_segv_handler();
diff --git a/pkg/csource/options.go b/pkg/csource/options.go
index 27529f429..01389240c 100644
--- a/pkg/csource/options.go
+++ b/pkg/csource/options.go
@@ -39,6 +39,7 @@ type Options struct {
 	CloseFDs     bool `json:"close_fds"`
 	KCSAN        bool `json:"kcsan,omitempty"`
 	DevlinkPCI   bool `json:"devlinkpci,omitempty"`
+	USB          bool `json:"usb,omitempty"`
 
 	UseTmpDir  bool `json:"tmpdir,omitempty"`
 	HandleSegv bool `json:"segv,omitempty"`
@@ -131,6 +132,9 @@ func (opts Options) checkLinuxOnly(OS string) error {
 	if opts.DevlinkPCI {
 		return fmt.Errorf("option DevlinkPCI is not supported on %v", OS)
 	}
+	if opts.USB {
+		return fmt.Errorf("option USB is not supported on %v", OS)
+	}
 	if opts.Sandbox == sandboxNamespace ||
 		(opts.Sandbox == sandboxSetuid && !(OS == openbsd || OS == freebsd || OS == netbsd)) ||
 		opts.Sandbox == sandboxAndroid {
@@ -171,6 +175,7 @@ func DefaultOpts(cfg *mgrconfig.Config) Options {
 		opts.BinfmtMisc = false
 		opts.CloseFDs = false
 		opts.DevlinkPCI = false
+		opts.USB = false
 	}
 	if cfg.Sandbox == "" || cfg.Sandbox == "setuid" {
 		opts.NetReset = false
@@ -250,6 +255,7 @@ func defaultFeatures(value bool) Features {
 		"binfmt_misc": {"setup binfmt_misc for testing", value},
 		"close_fds":   {"close fds after each program", value},
 		"devlink_pci": {"setup devlink PCI device", value},
+		"usb":         {"setup and use /dev/raw-gadget for USB emulation", value},
 	}
 }
 
diff --git a/pkg/csource/options_test.go b/pkg/csource/options_test.go
index b15783359..d4e1832e7 100644
--- a/pkg/csource/options_test.go
+++ b/pkg/csource/options_test.go
@@ -220,6 +220,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": true,
 			"close_fds":   true,
 			"devlink_pci": true,
+			"usb":         true,
 		}},
 		{"none", "none", false, map[string]bool{
 			"tun":         false,
@@ -229,6 +230,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": false,
 			"close_fds":   false,
 			"devlink_pci": false,
+			"usb":         false,
 		}},
 		{"all", "none", true, map[string]bool{
 			"tun":         true,
@@ -238,6 +240,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": true,
 			"close_fds":   true,
 			"devlink_pci": true,
+			"usb":         true,
 		}},
 		{"", "none", true, map[string]bool{
 			"tun":         false,
@@ -247,6 +250,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": false,
 			"close_fds":   false,
 			"devlink_pci": false,
+			"usb":         false,
 		}},
 		{"none", "all", true, map[string]bool{
 			"tun":         false,
@@ -256,6 +260,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": false,
 			"close_fds":   false,
 			"devlink_pci": false,
+			"usb":         false,
 		}},
 		{"none", "", true, map[string]bool{
 			"tun":         true,
@@ -265,6 +270,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": true,
 			"close_fds":   true,
 			"devlink_pci": true,
+			"usb":         true,
 		}},
 		{"tun,net_dev", "none", true, map[string]bool{
 			"tun":         true,
@@ -274,6 +280,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": false,
 			"close_fds":   false,
 			"devlink_pci": false,
+			"usb":         false,
 		}},
 		{"none", "cgroups,net_dev", true, map[string]bool{
 			"tun":         true,
@@ -283,6 +290,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": true,
 			"close_fds":   true,
 			"devlink_pci": true,
+			"usb":         true,
 		}},
 		{"close_fds", "none", true, map[string]bool{
 			"tun":         false,
@@ -292,6 +300,7 @@ func TestParseFeaturesFlags(t *testing.T) {
 			"binfmt_misc": false,
 			"close_fds":   true,
 			"devlink_pci": false,
+			"usb":         false,
 		}},
 	}
 	for i, test := range tests {
diff --git a/pkg/host/features.go b/pkg/host/features.go
index 3bc0127b6..707757755 100644
--- a/pkg/host/features.go
+++ b/pkg/host/features.go
@@ -25,6 +25,7 @@ const (
 	FeatureNetDevices
 	FeatureKCSAN
 	FeatureDevlinkPCI
+	FeatureUSBEmulation
 	numFeatures
 )
 
@@ -62,6 +63,7 @@ func Check(target *prog.Target) (*Features, error) {
 		FeatureNetDevices:       {Name: "net device setup", Reason: unsupported},
 		FeatureKCSAN:            {Name: "concurrency sanitizer", Reason: unsupported},
 		FeatureDevlinkPCI:       {Name: "devlink PCI setup", Reason: unsupported},
+		FeatureUSBEmulation:     {Name: "USB emulation", Reason: unsupported},
 	}
 	if targets.Get(target.OS, target.Arch).HostFuzzer {
 		return res, nil
@@ -99,6 +101,9 @@ func Setup(target *prog.Target, features *Features, featureFlags csource.Feature
 	if features[FeatureKCSAN].Enabled {
 		args = append(args, "kcsan")
 	}
+	if features[FeatureUSBEmulation].Enabled {
+		args = append(args, "usb")
+	}
 	_, err := osutil.RunCmd(time.Minute, "", executor, args...)
 	return err
 }
diff --git a/pkg/host/features_linux.go b/pkg/host/features_linux.go
index 7b4b7b243..8c6f63004 100644
--- a/pkg/host/features_linux.go
+++ b/pkg/host/features_linux.go
@@ -27,6 +27,7 @@ func init() {
 	checkFeature[FeatureNetDevices] = unconditionallyEnabled
 	checkFeature[FeatureKCSAN] = checkKCSAN
 	checkFeature[FeatureDevlinkPCI] = checkDevlinkPCI
+	checkFeature[FeatureUSBEmulation] = checkUSBEmulation
 }
 
 func checkCoverage() string {
@@ -183,7 +184,7 @@ func checkNetInjection() string {
 	return ""
 }
 
-func checkUSBInjection() string {
+func checkUSBEmulation() string {
 	if err := osutil.IsAccessible("/dev/raw-gadget"); err != nil {
 		return err.Error()
 	}
diff --git a/pkg/host/syscalls_linux.go b/pkg/host/syscalls_linux.go
index 693ec3f3e..dd89733c0 100644
--- a/pkg/host/syscalls_linux.go
+++ b/pkg/host/syscalls_linux.go
@@ -177,7 +177,7 @@ func isSupportedSyzkall(sandbox string, c *prog.Syscall) (bool, string) {
 		if !strings.Contains(fname, "#") {
 			panic(fmt.Sprintf("%v does not contain # in the file name (should be openat)", c.Name))
 		}
-		if checkUSBInjection() == "" {
+		if checkUSBEmulation() == "" {
 			// These entries might not be available at boot time,
 			// but will be created by connected USB devices.
 			USBDevicePrefixes := []string{
@@ -215,7 +215,7 @@ func isSupportedSyzkall(sandbox string, c *prog.Syscall) (bool, string) {
 		return reason == "", reason
 	case "syz_usb_connect", "syz_usb_connect_ath9k", "syz_usb_disconnect",
 		"syz_usb_control_io", "syz_usb_ep_write", "syz_usb_ep_read":
-		reason := checkUSBInjection()
+		reason := checkUSBEmulation()
 		return reason == "", reason
 	case "syz_kvm_setup_cpu":
 		switch c.Name {
diff --git a/pkg/repro/repro.go b/pkg/repro/repro.go
index 6de117df6..9c05f34ba 100644
--- a/pkg/repro/repro.go
+++ b/pkg/repro/repro.go
@@ -844,6 +844,7 @@ var cSimplifies = append(progSimplifies, []Simplify{
 		opts.BinfmtMisc = false
 		opts.CloseFDs = false
 		opts.DevlinkPCI = false
+		opts.USB = false
 		return true
 	},
 	func(opts *csource.Options) bool {
@@ -898,6 +899,13 @@ var cSimplifies = append(progSimplifies, []Simplify{
 		return true
 	},
 	func(opts *csource.Options) bool {
+		if !opts.USB {
+			return false
+		}
+		opts.USB = false
+		return true
+	},
+	func(opts *csource.Options) bool {
 		if !opts.UseTmpDir || opts.Sandbox == "namespace" || opts.Cgroups {
 			return false
 		}