3 files changed, 24 insertions, 2 deletions

diff --git a/sys/dev/mem/memdev.c b/sys/dev/mem/memdev.c
index 28ed6ebc4e93..37bad1538f7f 100644
--- a/sys/dev/mem/memdev.c
+++ b/sys/dev/mem/memdev.c
@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/memrange.h>
 #include <sys/module.h>
 #include <sys/mutex.h>
+#include <sys/priv.h>
 #include <sys/proc.h>
 #include <sys/signalvar.h>
 #include <sys/systm.h>
@@ -67,8 +68,14 @@ memopen(struct cdev *dev __unused, int flags, int fmt __unused,
 {
 	int error = 0;
 
-	if (flags & FWRITE)
-		error = securelevel_gt(td->td_ucred, 0);
+	if (flags & FREAD)
+		error = priv_check(td, PRIV_KMEM_READ);
+	if (flags & FWRITE) {
+		if (error == 0)
+			error = priv_check(td, PRIV_KMEM_WRITE);
+		if (error == 0)
+			error = securelevel_gt(td->td_ucred, 0);
+	}
 
 	return (error);
 }
diff --git a/sys/kern/kern_priv.c b/sys/kern/kern_priv.c
index fcd599393be4..204e00bb95e9 100644
--- a/sys/kern/kern_priv.c
+++ b/sys/kern/kern_priv.c
@@ -142,6 +142,15 @@ priv_check_cred(struct ucred *cred, int priv, int flags)
 	}
 
 	/*
+	 * Writes to kernel memory are a typical root-only operation,
+	 * but non-root users are expected to be able to read it.
+	 */
+	if (priv == PRIV_KMEM_READ) {
+		error = 0;
+		goto out;
+	}
+
+	/*
 	 * Now check with MAC, if enabled, to see if a policy module grants
 	 * privilege.
 	 */
diff --git a/sys/sys/priv.h b/sys/sys/priv.h
index b984f1a0beb4..de3f3bd03b1c 100644
--- a/sys/sys/priv.h
+++ b/sys/sys/priv.h
@@ -494,6 +494,12 @@
 #define	PRIV_RCTL_REMOVE_RULE	674
 
 /*
+ * Kernel memory privileges.
+ */
+#define	PRIV_KMEM_READ		680	/* Read from kernel memory. */
+#define	PRIV_KMEM_WRITE		681	/* Write to kernel memory. */
+
+/*
  * Track end of privilege list.
  */
 #define	_PRIV_HIGHEST		675