pkg/subsystem: fix dangling entries in the rules list

There was a mistake in the Linux subsystem generation rules that led to
the exclusion of exfat-related syz_mount_image calls from the resulting
subsystem descriptions.

Verify the rules before applying them. Fix other problems found by the
check.

4 files changed, 61 insertions, 26 deletions

diff --git a/pkg/subsystem/linux/rules.go b/pkg/subsystem/linux/rules.go
index 96de7e79d..1436668fa 100644
--- a/pkg/subsystem/linux/rules.go
+++ b/pkg/subsystem/linux/rules.go
@@ -23,19 +23,30 @@ type customRules struct {
 var (
 	linuxSubsystemRules = &customRules{
 		subsystemCalls: map[string][]string{
-			"adfs":      {"syz_mount_image$adfs"},
-			"affs":      {"syz_mount_image$affs"},
+			// TODO: we don't have subsystems for the following mount calls:
+			// - syz_mount_image$adfs
+			// - syz_mount_image$affs
+			// - syz_mount_image$befs
+			// - syz_mount_image$cramfs
+			// - syz_mount_image$efs
+			// - syz_mount_image$hpfs
+			// - syz_mount_image$minix
+			// - syz_mount_image$qnx4
+			// - syz_mount_image$qnx6
+			// - syz_mount_image$romfs
+			// - syz_mount_image$sysv
+			// - syz_mount_image$ufs
+			// - syz_mount_image$vxfs
+			// - syz_mount_image$zonefs
+
 			"bcachefs":  {"syz_mount_image$bcachefs"},
-			"befs":      {"syz_mount_image$befs"},
 			"bfs":       {"syz_mount_image$bfs"},
 			"bluetooth": {"syz_emit_vhci"},
 			"btrfs":     {"syz_mount_image$btrfs"},
-			"cramfs":    {"syz_mount_image$cramfs"},
-			"efs":       {"syz_mount_image$efs"},
 			"erofs":     {"syz_mount_image$erofs"},
 			"ext4":      {"syz_mount_image$ext4"},
 			"f2fs":      {"syz_mount_image$f2fs"},
-			"fat": {
+			"exfat": {
 				"syz_mount_image$msdos",
 				"syz_mount_image$vfat",
 				"syz_mount_image$exfat",
@@ -43,28 +54,20 @@ var (
 			"fuse":     {"syz_fuse_handle_req"},
 			"gfs2":     {"syz_mount_image$gfs2", "syz_mount_image$gfs2meta"},
 			"hfs":      {"syz_mount_image$hfs", "syz_mount_image$hfsplus"},
-			"hpfs":     {"syz_mount_image$hpfs"},
 			"input":    {"syz_usb_connect$hid"},
 			"io-uring": {"syz_io_uring_setup"},
 			"isofs":    {"syz_mount_image$iso9660"},
 			"jffs2":    {"syz_mount_image$jffs2"},
 			"jfs":      {"syz_mount_image$jfs"},
 			"kvm":      {"syz_kvm_setup_cpu", "syz_kvm_vgic_v3_setup", "syz_kvm_setup_syzos_vm", "syz_kvm_add_vcpu"},
-			"minix":    {"syz_mount_image$minix"},
 			"nilfs":    {"syz_mount_image$nilfs2"},
 			"ntfs3":    {"syz_mount_image$ntfs", "syz_mount_image$ntfs3"},
 			"ocfs2":    {"syz_mount_image$ocfs2"},
-			"omfs":     {"syz_mount_image$omfs"},
-			"qnx4":     {"syz_mount_image$qnx4"},
-			"qnx6":     {"syz_mount_image$qnx6"},
-			"reiserfs": {"syz_mount_image$reiserfs"},
-			"romfs":    {"syz_mount_image$romfs"},
+			"karma":    {"syz_mount_image$omfs"},
 			"squashfs": {"syz_mount_image$squashfs"},
-			"sysv":     {"syz_mount_image$sysv"},
-			"tmpfs":    {"syz_mount_image$tmpfs"},
-			"ubifs":    {"syz_mount_image$ubifs"},
+			"mm":       {"syz_mount_image$tmpfs"},
+			"mtd":      {"syz_mount_image$ubifs"},
 			"udf":      {"syz_mount_image$udf"},
-			"ufs":      {"syz_mount_image$ufs"},
 			"usb": {
 				"syz_usb_connect",
 				"syz_usb_connect$hid",
@@ -73,10 +76,8 @@ var (
 				"syz_usb_connect$cdc_ncm",
 				"syz_usb_connect$uac1",
 			},
-			"vxfs":     {"syz_mount_image$vxfs"},
 			"wireless": {"syz_80211_join_ibss", "syz_80211_inject_frame"},
 			"xfs":      {"syz_mount_image$xfs"},
-			"zonefs":   {"syz_mount_image$zonefs"},
 		},
 		notSubsystemEmails: map[string]struct{}{
 			"linaro-mm-sig@lists.linaro.org":      {},
diff --git a/pkg/subsystem/linux/subsystems.go b/pkg/subsystem/linux/subsystems.go
index 9da38d321..ae2c61556 100644
--- a/pkg/subsystem/linux/subsystems.go
+++ b/pkg/subsystem/linux/subsystems.go
@@ -141,6 +141,15 @@ func (ctx *linuxCtx) applyExtraRules(list []*subsystem.Subsystem) error {
 	if ctx.extraRules == nil {
 		return nil
 	}
+	if err := noDanglingRules(list, ctx.extraRules.subsystemCalls); err != nil {
+		return fmt.Errorf("subsystemCalls rules check failed: %w", err)
+	}
+	if err := noDanglingRules(list, ctx.extraRules.noReminders); err != nil {
+		return fmt.Errorf("noReminders rules check failed: %w", err)
+	}
+	if err := noDanglingRules(list, ctx.extraRules.noIndirectCc); err != nil {
+		return fmt.Errorf("noIndirectCc rules check failed: %w", err)
+	}
 	perName := map[string]*subsystem.Subsystem{}
 	for _, entry := range list {
 		entry.Syscalls = ctx.extraRules.subsystemCalls[entry.Name]
@@ -171,6 +180,28 @@ func (ctx *linuxCtx) applyExtraRules(list []*subsystem.Subsystem) error {
 	return nil
 }
 
+// Check that there are no rules that don't refer to any subsystem from the list.
+func noDanglingRules[T any](list []*subsystem.Subsystem, rules map[string]T) error {
+	usedRule := map[string]struct{}{}
+	for _, entry := range list {
+		if _, ok := rules[entry.Name]; !ok {
+			continue
+		}
+		usedRule[entry.Name] = struct{}{}
+	}
+	if len(usedRule) == len(rules) {
+		return nil
+	}
+	var dangling []string
+	for key := range rules {
+		if _, ok := usedRule[key]; ok {
+			continue
+		}
+		dangling = append(dangling, key)
+	}
+	return fmt.Errorf("unused keys: %q", dangling)
+}
+
 func mergeRawRecords(records []*maintainersRecord, email string) *subsystem.Subsystem {
 	var lists []string
 	subsystem := &subsystem.Subsystem{}
diff --git a/pkg/subsystem/linux/subsystems_test.go b/pkg/subsystem/linux/subsystems_test.go
index a3aa79b93..a411155ad 100644
--- a/pkg/subsystem/linux/subsystems_test.go
+++ b/pkg/subsystem/linux/subsystems_test.go
@@ -236,7 +236,6 @@ var (
 	testRules = &customRules{
 		subsystemCalls: map[string][]string{
 			"ext4":  {"syz_mount_image$ext4"},
-			"vxfs":  {"syz_mount_image$vxfs"},
 			"tmpfs": {"syz_mount_image$tmpfs"},
 		},
 		extraSubsystems: map[string][]string{
diff --git a/pkg/subsystem/lists/linux.go b/pkg/subsystem/lists/linux.go
index 27d8be5f6..ccc977b3d 100644
--- a/pkg/subsystem/lists/linux.go
+++ b/pkg/subsystem/lists/linux.go
@@ -1334,6 +1334,7 @@ func subsystems_linux() []*Subsystem {
 
 	exfat = Subsystem{
 		Name:        "exfat",
+		Syscalls:    []string{"syz_mount_image$msdos", "syz_mount_image$vfat", "syz_mount_image$exfat"},
 		Lists:       []string{"linux-fsdevel@vger.kernel.org"},
 		Maintainers: []string{"linkinjeon@kernel.org", "sj1557.seo@samsung.com"},
 		Parents:     []*Subsystem{&fs},
@@ -2158,6 +2159,7 @@ func subsystems_linux() []*Subsystem {
 
 	karma = Subsystem{
 		Name:        "karma",
+		Syscalls:    []string{"syz_mount_image$omfs"},
 		Lists:       []string{"linux-karma-devel@lists.sourceforge.net"},
 		Maintainers: []string{"me@bobcopeland.com"},
 		Parents:     []*Subsystem{&fs},
@@ -3019,9 +3021,10 @@ func subsystems_linux() []*Subsystem {
 	}
 
 	mm = Subsystem{
-		Name:    "mm",
-		Lists:   []string{"linux-mm@kvack.org"},
-		Parents: []*Subsystem{&kernel},
+		Name:     "mm",
+		Syscalls: []string{"syz_mount_image$tmpfs"},
+		Lists:    []string{"linux-mm@kvack.org"},
+		Parents:  []*Subsystem{&kernel},
 		PathRules: []PathRule{
 			{IncludeRegexp: "^arch/[^/]*/include/asm/percpu\\.h$|^include/linux/percpu[^/]*\\.h$|^lib/percpu[^/]*\\.c$|^mm/percpu[^/]*\\.c$"},
 			{IncludeRegexp: "^arch/[^/]*/include/asm/tlb\\.h$|^include/asm-generic/tlb\\.h$|^mm/mmu_gather\\.c$"},
@@ -3118,9 +3121,10 @@ func subsystems_linux() []*Subsystem {
 	}
 
 	mtd = Subsystem{
-		Name:    "mtd",
-		Lists:   []string{"linux-mtd@lists.infradead.org"},
-		Parents: []*Subsystem{&kernel},
+		Name:     "mtd",
+		Syscalls: []string{"syz_mount_image$ubifs"},
+		Lists:    []string{"linux-mtd@lists.infradead.org"},
+		Parents:  []*Subsystem{&kernel},
 		PathRules: []PathRule{
 			{IncludeRegexp: "^drivers/mtd/devices/block2mtd\\.c$"},
 			{IncludeRegexp: "^drivers/mtd/devices/docg3[^/]*$"},