devices: Use path to check device type

FreeBSD device numbers cannot be used to check the type of a device, as
they are merely unique filesystem IDs.

As the paths we use have been sanitized with realpath, we can simply use
the path to check if a requested file is an evdev or drm device. This
also allows us to make the check before the file is opened.

common/drm.c

@@ -1,10 +1,12 @@
+#include <string.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 
-#ifdef __linux__
+#if defined(__linux__)
 #include <sys/sysmacros.h>
 #endif
 
+#include "compiler.h"
 #include "drm.h"
 
 // From libdrm
@@ -21,6 +23,24 @@ int drm_drop_master(int fd) {
 	return ioctl(fd, DRM_IOCTL_DROP_MASTER, 0);
 }
 
+static int path_is_drm_card(const char *path) {
+	static const char prefix[] = "/dev/dri/card";
+	static const int prefixlen = STRLEN(prefix);
+	return strncmp(prefix, path, prefixlen) == 0;
+}
+
+static int path_is_drm_render(const char *path) {
+	static const char prefix[] = "/dev/dri/renderD";
+	static const int prefixlen = STRLEN(prefix);
+	return strncmp(prefix, path, prefixlen) == 0;
+}
+
+int path_is_drm(const char *path) {
+	return path_is_drm_card(path) || path_is_drm_render(path);
+}
+
+#if defined(__linux__)
 int dev_is_drm(dev_t device) {
 	return major(device) == 226;
 }
+#endif

common/evdev.c

@@ -1,9 +1,11 @@
 #include <stdlib.h>
+#include <string.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 
 #if defined(__linux__)
 #include <linux/input.h>
+#include <linux/major.h>
 #include <sys/sysmacros.h>
 #elif defined(__FreeBSD__)
 #include <dev/evdev/input.h>
@@ -11,12 +13,21 @@
 #error Unsupported platform
 #endif
 
+#include "compiler.h"
 #include "evdev.h"
 
+int path_is_evdev(const char *path) {
+	static const char prefix[] = "/dev/input/event";
+	static const size_t prefixlen = STRLEN(prefix);
+	return strncmp(prefix, path, prefixlen) == 0;
+}
+
 int evdev_revoke(int fd) {
 	return ioctl(fd, EVIOCREVOKE, NULL);
 }
 
+#if defined(__linux__)
 int dev_is_evdev(dev_t device) {
-	return major(device) == 13;
+	return major(device) == INPUT_MAJOR;
 }
+#endif

include/compiler.h

@@ -15,4 +15,6 @@
 #define ALWAYS_INLINE inline
 #endif
 
+#define STRLEN(s) ((sizeof(s) / sizeof(s[0])) - 1)
+
 #endif

include/drm.h

@@ -1,10 +1,13 @@
 #ifndef _SEATD_DRM_H
 #define _SEATD_DRM_H
 
-#include <sys/types.h>
-
 int drm_set_master(int fd);
 int drm_drop_master(int fd);
+int path_is_drm(const char *path);
+
+#if defined(__linux__)
+#include <sys/types.h>
 int dev_is_drm(dev_t device);
+#endif
 
 #endif

include/evdev.h

@@ -1,9 +1,12 @@
 #ifndef _SEATD_EVDEV_H
 #define _SEATD_EVDEV_H
 
-#include <sys/types.h>
-
 int evdev_revoke(int fd);
+int path_is_evdev(const char *path);
+
+#if defined(__linux__)
+#include <sys/types.h>
 int dev_is_evdev(dev_t device);
+#endif
 
 #endif

include/seat.h

@@ -8,13 +8,19 @@
 
 struct client;
 
+enum seat_device_type {
+	SEAT_DEVICE_TYPE_NORMAL,
+	SEAT_DEVICE_TYPE_EVDEV,
+	SEAT_DEVICE_TYPE_DRM,
+};
+
 struct seat_device {
 	int device_id;
 	int fd;
 	int ref_cnt;
 	bool active;
 	char *path;
-	dev_t dev;
+	enum seat_device_type type;
 };
 
 struct seat {

seatd/seat.c

@@ -141,6 +141,17 @@ struct seat_device *seat_open_device(struct client *client, const char *path) {
 		return NULL;
 	}
 
+	enum seat_device_type type;
+	if (path_is_evdev(sanitized_path)) {
+		type = SEAT_DEVICE_TYPE_EVDEV;
+	} else if (path_is_drm(sanitized_path)) {
+		type = SEAT_DEVICE_TYPE_DRM;
+	} else {
+		log_errorf("invalid path '%s'", sanitized_path);
+		errno = ENOENT;
+		return NULL;
+	}
+
 	int device_id = 1;
 	for (size_t idx = 0; idx < client->devices.length; idx++) {
 		struct seat_device *device = client->devices.items[idx];
@@ -164,39 +175,24 @@ struct seat_device *seat_open_device(struct client *client, const char *path) {
 		return NULL;
 	}
 
-	const char *prefix = "/dev/";
-	if (strncmp(prefix, sanitized_path, strlen(prefix)) != 0) {
-		log_errorf("invalid path '%s': expected device in /dev", sanitized_path);
-		errno = ENOENT;
-		return NULL;
-	}
-
 	int fd = open(sanitized_path, O_RDWR | O_NOCTTY | O_NOFOLLOW | O_CLOEXEC | O_NONBLOCK);
 	if (fd == -1) {
 		log_errorf("could not open file: %s", strerror(errno));
 		return NULL;
 	}
 
-	struct stat st;
+	switch (type) {
-	if (fstat(fd, &st) == -1) {
+	case SEAT_DEVICE_TYPE_DRM:
-		log_errorf("could not fstat: %s", strerror(errno));
-		close(fd);
-		errno = EACCES;
-		return NULL;
-	}
-
-	if (dev_is_drm(st.st_rdev)) {
 		if (drm_set_master(fd) == -1) {
 			log_debugf("drm_set_master failed: %s", strerror(errno));
 		}
-	} else if (dev_is_evdev(st.st_rdev)) {
+		break;
+	case SEAT_DEVICE_TYPE_EVDEV:
 		// Nothing to do here
-	} else {
+		break;
-		// Not a device type we want to share
+	default:
-		log_errorf("disallowed device type for '%s': %ld", sanitized_path, st.st_rdev);
+		log_error("invalid seat device type");
-		close(fd);
+		abort();
-		errno = EACCES;
-		return NULL;
 	}
 
 	struct seat_device *device = calloc(1, sizeof(struct seat_device));
@@ -218,8 +214,8 @@ struct seat_device *seat_open_device(struct client *client, const char *path) {
 	log_debugf("seat: %p, client: %p, path: '%s', device_id: %d", (void *)seat, (void *)client,
 		   path, device_id);
 
-	device->ref_cnt++;
+	device->ref_cnt = 1;
-	device->dev = st.st_rdev;
+	device->type = type;
 	device->fd = fd;
 	device->device_id = device_id;
 	device->active = true;
@@ -252,14 +248,20 @@ int seat_close_device(struct client *client, struct seat_device *seat_device) {
 	// The ref count hit zero, so destroy the device
 	list_del(&client->devices, idx);
 	if (seat_device->active && seat_device->fd != -1) {
-		if (dev_is_drm(seat_device->dev)) {
+		switch (seat_device->type) {
+		case SEAT_DEVICE_TYPE_DRM:
 			if (drm_drop_master(seat_device->fd) == -1) {
 				log_debugf("drm_drop_master failed: %s", strerror(errno));
 			}
-		} else if (dev_is_evdev(seat_device->dev)) {
+			break;
+		case SEAT_DEVICE_TYPE_EVDEV:
 			if (evdev_revoke(seat_device->fd) == -1) {
 				log_debugf("evdev_revoke failed: %s", strerror(errno));
 			}
+			break;
+		default:
+			log_error("invalid seat device type");
+			abort();
 		}
 		close(seat_device->fd);
 		seat_device->fd = -1;
@@ -277,17 +279,22 @@ static int seat_deactivate_device(struct client *client, struct seat_device *sea
 	if (!seat_device->active) {
 		return 0;
 	}
-	if (dev_is_drm(seat_device->dev)) {
+	switch (seat_device->type) {
+	case SEAT_DEVICE_TYPE_DRM:
 		if (drm_drop_master(seat_device->fd) == -1) {
+			log_debugf("drm_drop_master failed: %s", strerror(errno));
 			return -1;
 		}
-	} else if (dev_is_evdev(seat_device->dev)) {
+		break;
+	case SEAT_DEVICE_TYPE_EVDEV:
 		if (evdev_revoke(seat_device->fd) == -1) {
+			log_debugf("evdev_revoke failed: %s", strerror(errno));
 			return -1;
 		}
-	} else {
+		break;
-		errno = EACCES;
+	default:
-		return -1;
+		log_error("invalid seat device type");
+		abort();
 	}
 	seat_device->active = false;
 	return 0;
@@ -301,17 +308,21 @@ static int seat_activate_device(struct client *client, struct seat_device *seat_
 	if (seat_device->active) {
 		return 0;
 	}
-	if (dev_is_drm(seat_device->dev)) {
+	switch (seat_device->type) {
-		drm_set_master(seat_device->fd);
+	case SEAT_DEVICE_TYPE_DRM:
+		if (drm_set_master(seat_device->fd) == -1) {
+			log_debugf("drmset_master failed: %s", strerror(errno));
+		}
 		seat_device->active = true;
-	} else if (dev_is_evdev(seat_device->dev)) {
+		break;
-		// We can't do anything here
+	case SEAT_DEVICE_TYPE_EVDEV:
 		errno = EINVAL;
 		return -1;
-	} else {
+	default:
-		errno = EACCES;
+		log_error("invalid seat device type");
-		return -1;
+		abort();
 	}
+
 	return 0;
 }