media: rc: bpf attach/detach requires write permission

Note that bpf attach/detach also requires CAP_NET_ADMIN.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/rc/bpf-lirc.c

@@ -253,7 +253,7 @@ int lirc_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 	if (attr->attach_flags)
 		return -EINVAL;
 
-	rcdev = rc_dev_get_from_fd(attr->target_fd);
+	rcdev = rc_dev_get_from_fd(attr->target_fd, true);
 	if (IS_ERR(rcdev))
 		return PTR_ERR(rcdev);
 
@@ -278,7 +278,7 @@ int lirc_prog_detach(const union bpf_attr *attr)
 	if (IS_ERR(prog))
 		return PTR_ERR(prog);
 
-	rcdev = rc_dev_get_from_fd(attr->target_fd);
+	rcdev = rc_dev_get_from_fd(attr->target_fd, true);
 	if (IS_ERR(rcdev)) {
 		bpf_prog_put(prog);
 		return PTR_ERR(rcdev);
@@ -303,7 +303,7 @@ int lirc_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
 	if (attr->query.query_flags)
 		return -EINVAL;
 
-	rcdev = rc_dev_get_from_fd(attr->query.target_fd);
+	rcdev = rc_dev_get_from_fd(attr->query.target_fd, false);
 	if (IS_ERR(rcdev))
 		return PTR_ERR(rcdev);
 

drivers/media/rc/lirc_dev.c

@@ -814,7 +814,7 @@ void __exit lirc_dev_exit(void)
 	unregister_chrdev_region(lirc_base_dev, RC_DEV_MAX);
 }
 
-struct rc_dev *rc_dev_get_from_fd(int fd)
+struct rc_dev *rc_dev_get_from_fd(int fd, bool write)
 {
 	struct fd f = fdget(fd);
 	struct lirc_fh *fh;
@@ -828,6 +828,9 @@ struct rc_dev *rc_dev_get_from_fd(int fd)
 		return ERR_PTR(-EINVAL);
 	}
 
+	if (write && !(f.file->f_mode & FMODE_WRITE))
+		return ERR_PTR(-EPERM);
+
 	fh = f.file->private_data;
 	dev = fh->rc;
 

drivers/media/rc/rc-core-priv.h

@@ -325,7 +325,7 @@ void lirc_raw_event(struct rc_dev *dev, struct ir_raw_event ev);
 void lirc_scancode_event(struct rc_dev *dev, struct lirc_scancode *lsc);
 int lirc_register(struct rc_dev *dev);
 void lirc_unregister(struct rc_dev *dev);
-struct rc_dev *rc_dev_get_from_fd(int fd);
+struct rc_dev *rc_dev_get_from_fd(int fd, bool write);
 #else
 static inline int lirc_dev_init(void) { return 0; }
 static inline void lirc_dev_exit(void) {}