From: Vitaliy Makkoveev <mvs@openbsd.org>
Subject: sysctl(2): unlock sysctl_video()
To: tech@openbsd.org
Date: Thu, 22 Aug 2024 13:34:52 +0300

Like recently unlocked sysctl_audio(), it is the only KERN_VIDEO_RECORD.
`video_record_enable' is atomically accessed integer.

Index: sys/dev/video.c
===================================================================
RCS file: /cvs/src/sys/dev/video.c,v
diff -u -p -r1.57 video.c
--- sys/dev/video.c	2 Jul 2022 08:50:41 -0000	1.57
+++ sys/dev/video.c	22 Aug 2024 10:28:56 -0000
@@ -34,6 +34,11 @@
 
 #include <uvm/uvm_extern.h>
 
+/*
+ * Locks used to protect data:
+ *	a	atomic
+ */
+
 #ifdef VIDEO_DEBUG
 int video_debug = 1;
 #define DPRINTF(l, x...) do { if ((l) <= video_debug) printf(x); } while (0)
@@ -85,7 +90,7 @@ struct cfdriver video_cd = {
 /*
  * Global flag to control if video recording is enabled by kern.video.record.
  */
-int video_record_enable = 0;
+int video_record_enable = 0;	/* [a] */
 
 int
 videoprobe(struct device *parent, void *match, void *aux)
@@ -216,7 +221,7 @@ videoread(dev_t dev, struct uio *uio, in
 
 	/* move no more than 1 frame to userland, as per specification */
 	size = ulmin(uio->uio_resid, sc->sc_fsize);
-	if (!video_record_enable)
+	if (atomic_load_int(&video_record_enable) == 0)
 		bzero(sc->sc_fbuffer, size);
 	error = uiomove(sc->sc_fbuffer, size, uio);
 	sc->sc_frames_ready--;
@@ -354,7 +359,7 @@ videoioctl(dev_t dev, u_long cmd, caddr_
 		}
 		error = (sc->hw_if->dqbuf)(sc->hw_hdl,
 		    (struct v4l2_buffer *)data);
-		if (!video_record_enable)
+		if (atomic_load_int(&video_record_enable) == 0)
 			bzero(sc->sc_fbuffer_mmap + vb->m.offset, vb->length);
 		sc->sc_frames_ready--;
 		break;
Index: sys/kern/kern_sysctl.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_sysctl.c,v
diff -u -p -r1.442 kern_sysctl.c
--- sys/kern/kern_sysctl.c	20 Aug 2024 13:29:25 -0000	1.442
+++ sys/kern/kern_sysctl.c	22 Aug 2024 10:28:57 -0000
@@ -455,11 +455,6 @@ kern_sysctl_dirs(int top_name, int *name
 		return witness_sysctl(name, namelen, oldp, oldlenp,
 		    newp, newlen);
 #endif
-#if NVIDEO > 0
-	case KERN_VIDEO:
-		return (sysctl_video(name, namelen, oldp, oldlenp,
-		    newp, newlen));
-#endif
 	case KERN_CPUSTATS:
 		return (sysctl_cpustats(name, namelen, oldp, oldlenp,
 		    newp, newlen));
@@ -487,6 +482,11 @@ kern_sysctl(int *name, u_int namelen, vo
 #if NAUDIO > 0
 		case KERN_AUDIO:
 			return (sysctl_audio(name, namelen, oldp, oldlenp,
+			    newp, newlen));
+#endif
+#if NVIDEO > 0
+		case KERN_VIDEO:
+			return (sysctl_video(name, namelen, oldp, oldlenp,
 			    newp, newlen));
 #endif
 		default: