Index: sys/compat/cloudabi/cloudabi_mem.c
===================================================================
--- sys/compat/cloudabi/cloudabi_mem.c
+++ sys/compat/cloudabi/cloudabi_mem.c
@@ -110,8 +110,8 @@
 	if (error != 0)
 		return (error);
 
-	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, prot, flags,
-	    uap->fd, uap->off));
+	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len,
+	    PROT_MAX(PROT_ALL) | prot, flags, uap->fd, uap->off));
 }
 
 int
Index: sys/compat/freebsd32/freebsd32_misc.c
===================================================================
--- sys/compat/freebsd32/freebsd32_misc.c
+++ sys/compat/freebsd32/freebsd32_misc.c
@@ -471,8 +471,8 @@
 		prot |= PROT_EXEC;
 #endif
 
-	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, prot,
-	    uap->flags, uap->fd, PAIR32TO64(off_t, uap->pos)));
+	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, prot, uap->flags,
+	    uap->fd, PAIR32TO64(off_t, uap->pos)));
 }
 
 #ifdef COMPAT_FREEBSD6
@@ -488,8 +488,9 @@
 		prot |= PROT_EXEC;
 #endif
 
-	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, prot,
-	    uap->flags, uap->fd, PAIR32TO64(off_t, uap->pos)));
+	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len,
+	    PROT_MAX(PROT_ALL) | prot, uap->flags, uap->fd,
+	    PAIR32TO64(off_t, uap->pos)));
 }
 #endif
 
Index: sys/compat/linux/linux_mmap.c
===================================================================
--- sys/compat/linux/linux_mmap.c
+++ sys/compat/linux/linux_mmap.c
@@ -211,13 +211,14 @@
 	 */
 	if (addr != 0 && (bsd_flags & MAP_FIXED) == 0 &&
 	    (bsd_flags & MAP_EXCL) == 0) {
-		error = kern_mmap(td, addr, len, prot,
+		error = kern_mmap(td, addr, len, PROT_MAX(PROT_ALL) | prot,
 		    bsd_flags | MAP_FIXED | MAP_EXCL, fd, pos);
 		if (error == 0)
 			goto out;
 	}
 
-	error = kern_mmap(td, addr, len, prot, bsd_flags, fd, pos);
+	error = kern_mmap(td, addr, len, PROT_MAX(PROT_ALL) | prot, bsd_flags,
+	    fd, pos);
 out:
 	LINUX_CTR2(mmap2, "return: %d (%p)", error, td->td_retval[0]);
 
Index: sys/sys/mman.h
===================================================================
--- sys/sys/mman.h
+++ sys/sys/mman.h
@@ -55,6 +55,16 @@
 #define	PROT_READ	0x01	/* pages can be read */
 #define	PROT_WRITE	0x02	/* pages can be written */
 #define	PROT_EXEC	0x04	/* pages can be executed */
+#if __BSD_VISIBLE
+#define	_PROT_ALL	(PROT_READ|PROT_WRITE|PROT_EXEC)
+#define	EXTRACT_PROT(prot)	(prot & _PROT_ALL)
+
+#define	_PROT_MAX_SHIFT	16
+#define	PROT_MAX(prot)	((prot) << _PROT_MAX_SHIFT)
+#define	EXTRACT_PROT_MAX(prot)						\
+	(((prot) >> _PROT_MAX_SHIFT) != 0 ?				\
+	 ((prot) >> _PROT_MAX_SHIFT) : EXTRACT_PROT(prot))
+#endif
 
 /*
  * Flags contain sharing type and options.
Index: sys/vm/vm_mmap.c
===================================================================
--- sys/vm/vm_mmap.c
+++ sys/vm/vm_mmap.c
@@ -184,9 +184,12 @@
 	vm_offset_t addr;
 	vm_size_t pageoff;
 	vm_prot_t cap_maxprot;
-	int align, error;
+	int align, error, max_prot;
 	cap_rights_t rights;
 
+	max_prot = EXTRACT_PROT_MAX(prot);
+	prot = EXTRACT_PROT(prot);
+
 	vms = td->td_proc->p_vmspace;
 	fp = NULL;
 	AUDIT_ARG_FD(fd);
@@ -329,7 +332,7 @@
 		 * This relies on VM_PROT_* matching PROT_*.
 		 */
 		error = vm_mmap_object(&vms->vm_map, &addr, size, prot,
-		    VM_PROT_ALL, flags, NULL, pos, FALSE, td);
+		    max_prot, flags, NULL, pos, FALSE, td);
 	} else {
 		/*
 		 * Mapping file, get fp for validation and don't let the
@@ -357,7 +360,7 @@
 
 		/* This relies on VM_PROT_* matching PROT_*. */
 		error = fo_mmap(fp, &vms->vm_map, &addr, size, prot,
-		    cap_maxprot, flags, pos, td);
+		    max_prot & cap_maxprot, flags, pos, td);
 	}
 
 	if (error == 0)
@@ -374,8 +377,8 @@
 freebsd6_mmap(struct thread *td, struct freebsd6_mmap_args *uap)
 {
 
-	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, uap->prot,
-	    uap->flags, uap->fd, uap->pos));
+	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len,
+	    PROT_MAX(PROT_ALL) | uap->prot, uap->flags, uap->fd, uap->pos));
 }
 #endif
 
@@ -429,8 +432,8 @@
 		flags |= MAP_PRIVATE;
 	if (uap->flags & OMAP_FIXED)
 		flags |= MAP_FIXED;
-	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len, prot, flags,
-	    uap->fd, uap->pos));
+	return (kern_mmap(td, (uintptr_t)uap->addr, uap->len,
+	    PROT_MAX(PROT_ALL) | prot, flags, uap->fd, uap->pos));
 }
 #endif				/* COMPAT_43 */