cgroups/devices: introduce ebpf device cgroup global rule types

src/lxc/cgroups/cgfsng.c

@@ -2303,11 +2303,13 @@ static int device_cgroup_rule_parse(struct device_item *device, const char *key,
 		device->type = 'a';
 		device->major = -1;
 		device->minor = -1;
-		device->global_rule = device->allow;
+		device->global_rule = device->allow
+					  ? LXC_BPF_DEVICE_CGROUP_BLACKLIST
+					  : LXC_BPF_DEVICE_CGROUP_WHITELIST;
 		device->allow = -1;
 		return 0;
 	} else {
-		device->global_rule = -1;
+		device->global_rule = LXC_BPF_DEVICE_CGROUP_LOCAL_RULE;
 	}
 
 	switch (*val) {

src/lxc/cgroups/cgroup2_devices.c

@@ -173,6 +173,10 @@ struct bpf_program *bpf_program_new(uint32_t prog_type)
 
 	prog->prog_type = prog_type;
 	prog->kernel_fd = -EBADF;
+	/*
+	 * By default a whitelist is used unless the user tells us otherwise.
+	 */
+	prog->device_list_type = LXC_BPF_DEVICE_CGROUP_WHITELIST;
 
 	return move_ptr(prog);
 }
@@ -216,8 +220,8 @@ int bpf_program_append_device(struct bpf_program *prog, struct device_item *devi
 		return minus_one_set_errno(EINVAL);
 
 	/* This is a global rule so no need to append anything. */
-	if (device->global_rule >= 0) {
-		prog->blacklist = device->global_rule;
+	if (device->global_rule > LXC_BPF_DEVICE_CGROUP_LOCAL_RULE) {
+		prog->device_list_type = device->global_rule;
 		return 0;
 	}
 
@@ -292,7 +296,7 @@ int bpf_program_append_device(struct bpf_program *prog, struct device_item *devi
 int bpf_program_finalize(struct bpf_program *prog)
 {
 	struct bpf_insn ins[] = {
-	    BPF_MOV64_IMM(BPF_REG_0, prog->blacklist ? 1 : 0),
+	    BPF_MOV64_IMM(BPF_REG_0, prog->device_list_type),
 	    BPF_EXIT_INSN(),
 	};
 
@@ -300,7 +304,9 @@ int bpf_program_finalize(struct bpf_program *prog)
 		return minus_one_set_errno(EINVAL);
 
 	TRACE("Implementing %s bpf device cgroup program",
-	      prog->blacklist ? "blacklist" : "whitelist");
+	      prog->device_list_type == LXC_BPF_DEVICE_CGROUP_BLACKLIST
+		  ? "blacklist"
+		  : "whitelist");
 	return bpf_program_add_instructions(prog, ins, ARRAY_SIZE(ins));
 }
 
@@ -443,9 +449,12 @@ int bpf_list_add_device(struct lxc_conf *conf, struct device_item *device)
 
 		if (cur->global_rule != -1 && device->global_rule != -1) {
 			TRACE("Switched from %s to %s",
-			      cur->global_rule == 0 ? "whitelist" : "blacklist",
-			      device->global_rule == 0 ? "whitelist"
-						       : "blacklist");
+			      cur->global_rule == LXC_BPF_DEVICE_CGROUP_WHITELIST
+				  ? "whitelist"
+				  : "blacklist",
+			      device->global_rule == LXC_BPF_DEVICE_CGROUP_WHITELIST
+				  ? "whitelist"
+				  : "blacklist");
 			cur->global_rule = device->global_rule;
 			return 1;
 		}

src/lxc/cgroups/cgroup2_devices.h

@@ -63,7 +63,7 @@ static inline int missing_bpf(int cmd, union bpf_attr *attr, size_t size)
 #endif
 
 struct bpf_program {
-	bool blacklist;
+	int device_list_type;
 	int kernel_fd;
 	uint32_t prog_type;
 

src/lxc/conf.h

@@ -223,15 +223,22 @@ struct lxc_state_client {
 	lxc_state_t states[MAX_STATE];
 };
 
+enum {
+	LXC_BPF_DEVICE_CGROUP_WHITELIST  =  0,
+	LXC_BPF_DEVICE_CGROUP_BLACKLIST  =  1,
+	LXC_BPF_DEVICE_CGROUP_LOCAL_RULE = -1,
+};
+
 struct device_item {
 	char type;
 	int major;
 	int minor;
 	char access[4];
 	int allow;
-	/* -1 -> no global rule
-	 *  0 -> whitelist (deny all)
-	 *  1 -> blacklist (allow all)
+	/*
+	 * LXC_BPF_DEVICE_CGROUP_LOCAL_RULE -> no global rule
+	 * LXC_BPF_DEVICE_CGROUP_WHITELIST  -> whitelist (deny all)
+	 * LXC_BPF_DEVICE_CGROUP_BLACKLIST  -> blacklist (allow all)
 	 */
 	int global_rule;
 };