udev: allow final assignments :=

The use of KEY:=<value> will make the key unchangeable by later rules.

Signed-off-by: Kay Sievers <kay.sievers@suse.de>

test/udev-test.pl

@@ -1304,6 +1304,29 @@ EOF
 KERNEL=="sda", NAME="ok2", RUN+="/bin/ln -s ok2 %r/testsymlink2"
 KERNEL=="sda", ACTION=="remove", RUN+="/bin/rm -f %r/testsymlink2"
 KERNEL=="sda", NAME="not-ok2"
+EOF
+	},
+	{
+		desc		=> "final assignment",
+		subsys		=> "block",
+		devpath		=> "/block/sda",
+		exp_name	=> "ok",
+		exp_perms	=> "root:nobody:0640",
+		rules		=> <<EOF
+KERNEL=="sda", GROUP:="nobody"
+KERNEL=="sda", GROUP="not-ok", MODE="0640", NAME="ok"
+EOF
+	},
+	{
+		desc		=> "final assignment",
+		subsys		=> "block",
+		devpath		=> "/block/sda",
+		exp_name	=> "ok",
+		exp_perms	=> "root:nobody:0640",
+		rules		=> <<EOF
+KERNEL=="sda", GROUP:="nobody"
+SUBSYSTEM=="block", MODE:="640"
+KERNEL=="sda", GROUP="not-ok", MODE="0666", NAME="ok"
 EOF
 	},
 );

udev.h

@@ -64,11 +64,16 @@ struct udevice {
 	char name[PATH_SIZE];
 	char devname[PATH_SIZE];
 	struct list_head symlink_list;
+	int symlink_final;
 	char owner[USER_SIZE];
+	int owner_final;
 	char group[USER_SIZE];
+	int group_final;
 	mode_t mode;
+	int mode_final;
 	dev_t devt;
 	struct list_head run_list;
+	int run_final;
 
 	char tmp_node[PATH_SIZE];
 	int partitions;

udev_rules.c

@@ -754,26 +754,34 @@ int udev_rules_get_name(struct udevice *udev, struct sysfs_class_device *class_d
 			}
 
 			/* apply permissions */
-			if (rule->mode != 0000) {
+			if (!udev->mode_final && rule->mode != 0000) {
+				if (rule->mode_operation == KEY_OP_ASSIGN_FINAL)
+					udev->mode_final = 1;
 				udev->mode = rule->mode;
 				dbg("applied mode=%#o to '%s'", udev->mode, udev->kernel_name);
 			}
-			if (rule->owner[0] != '\0') {
+			if (!udev->owner_final && rule->owner[0] != '\0') {
+				if (rule->owner_operation == KEY_OP_ASSIGN_FINAL)
+					udev->owner_final = 1;
 				strlcpy(udev->owner, rule->owner, sizeof(udev->owner));
 				apply_format(udev, udev->owner, sizeof(udev->owner), class_dev, sysfs_device);
 				dbg("applied owner='%s' to '%s'", udev->owner, udev->kernel_name);
 			}
-			if (rule->group[0] != '\0') {
+			if (!udev->group_final && rule->group[0] != '\0') {
+				if (rule->group_operation == KEY_OP_ASSIGN_FINAL)
+					udev->group_final = 1;
 				strlcpy(udev->group, rule->group, sizeof(udev->group));
 				apply_format(udev, udev->group, sizeof(udev->group), class_dev, sysfs_device);
 				dbg("applied group='%s' to '%s'", udev->group, udev->kernel_name);
 			}
 
 			/* collect symlinks */
-			if (rule->symlink[0] != '\0') {
+			if (!udev->symlink_final && rule->symlink[0] != '\0') {
 				char temp[PATH_SIZE];
 				char *pos, *next;
 
+				if (rule->symlink_operation == KEY_OP_ASSIGN_FINAL)
+					udev->symlink_final = 1;
 				info("configured rule in '%s[%i]' applied, added symlink '%s'",
 				     rule->config_file, rule->config_line, rule->symlink);
 				strlcpy(temp, rule->symlink, sizeof(temp));
@@ -808,9 +816,11 @@ int udev_rules_get_name(struct udevice *udev, struct sysfs_class_device *class_d
 					    udev->name, udev->owner, udev->group, udev->mode, udev->partitions);
 			}
 
-			if (rule->run[0] != '\0') {
+			if (!udev->run_final && rule->run[0] != '\0') {
 				char program[PATH_SIZE];
 
+				if (rule->run_operation == KEY_OP_ASSIGN_FINAL)
+					udev->run_final = 1;
 				strlcpy(program, rule->run, sizeof(program));
 				apply_format(udev, program, sizeof(program), class_dev, sysfs_device);
 				dbg("add run '%s'", program);

udev_rules.h

@@ -62,6 +62,7 @@ enum key_operation {
 	KEY_OP_NOMATCH,
 	KEY_OP_ADD,
 	KEY_OP_ASSIGN,
+	KEY_OP_ASSIGN_FINAL,
 };
 
 struct key_pair {
@@ -96,10 +97,15 @@ struct udev_rule {
 
 	char name[PATH_SIZE];
 	char symlink[PATH_SIZE];
+	enum key_operation symlink_operation;
 	char owner[USER_SIZE];
+	enum key_operation owner_operation;
 	char group[USER_SIZE];
+	enum key_operation group_operation;
 	mode_t mode;
+	enum key_operation mode_operation;
 	char run[PATH_SIZE];
+	enum key_operation run_operation;
 
 	int last_rule;
 	int ignore_device;

udev_rules_parse.c

@@ -89,6 +89,8 @@ static int get_key(char **line, char **key, enum key_operation *operation, char
 			break;
 		if (linepos[0] == '!')
 			break;
+		if (linepos[0] == ':')
+			break;
 	}
 
 	/* remember end of key */
@@ -115,6 +117,10 @@ static int get_key(char **line, char **key, enum key_operation *operation, char
 		*operation = KEY_OP_ASSIGN;
 		linepos++;
 		dbg("operator=assign");
+	} else if (linepos[0] == ':' && linepos[1] == '=') {
+		*operation = KEY_OP_ASSIGN_FINAL;
+		linepos += 2;
+		dbg("operator=assign_final");
 	} else
 		return -1;
 
@@ -364,30 +370,35 @@ static int rules_parse(const char *filename)
 
 			if (strcasecmp(key, KEY_SYMLINK) == 0) {
 				strlcpy(rule.symlink, value, sizeof(rule.symlink));
+				rule.symlink_operation = operation;
 				valid = 1;
 				continue;
 			}
 
 			if (strcasecmp(key, KEY_OWNER) == 0) {
 				strlcpy(rule.owner, value, sizeof(rule.owner));
+				rule.owner_operation = operation;
 				valid = 1;
 				continue;
 			}
 
 			if (strcasecmp(key, KEY_GROUP) == 0) {
 				strlcpy(rule.group, value, sizeof(rule.group));
+				rule.group_operation = operation;
 				valid = 1;
 				continue;
 			}
 
 			if (strcasecmp(key, KEY_MODE) == 0) {
 				rule.mode = strtol(value, NULL, 8);
+				rule.mode_operation = operation;
 				valid = 1;
 				continue;
 			}
 
 			if (strcasecmp(key, KEY_RUN) == 0) {
 				strlcpy(rule.run, value, sizeof(rule.run));
+				rule.run_operation = operation;
 				valid = 1;
 				continue;
 			}