Extend uvm_map_hint() to get an address range as extra arguments, and make

sure it will return an address within that range.

Use this in uaddr_rnd_select() to make sure we will not attempt to pick
an address beyond what we are allowed to map.

In my trees for 9 months, blackmailed s2k15 attendees into agreeing now would
be a good time to commit.

4 files changed, 22 insertions, 12 deletions

diff --git a/sys/uvm/uvm_addr.c b/sys/uvm/uvm_addr.c
index e3f39b32105..5b153ed5ba0 100644
--- a/sys/uvm/uvm_addr.c
+++ b/sys/uvm/uvm_addr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_addr.c,v 1.12 2015/03/30 21:05:17 miod Exp $	*/
+/*	$OpenBSD: uvm_addr.c,v 1.13 2015/03/30 21:08:40 miod Exp $	*/
 
 /*
  * Copyright (c) 2011 Ariane van der Steldt <ariane@stack.nl>
@@ -564,6 +564,7 @@ uaddr_rnd_select(struct vm_map *map, struct uvm_addr_state *uaddr,
     vm_prot_t prot, vaddr_t hint)
 {
 	struct vmspace		*vm;
+	vaddr_t			 minaddr, maxaddr;
 	vaddr_t			 guard_sz;
 	vaddr_t			 low_addr, high_addr;
 	struct vm_map_entry	*entry, *next;
@@ -576,22 +577,25 @@ uaddr_rnd_select(struct vm_map *map, struct uvm_addr_state *uaddr,
 	/* Deal with guardpages: search for space with one extra page. */
 	guard_sz = ((map->flags & VM_MAP_GUARDPAGES) == 0 ? 0 : PAGE_SIZE);
 
+	minaddr = uvm_addr_align_forward(uaddr->uaddr_minaddr, align, offset);
+	maxaddr = uvm_addr_align_backward(uaddr->uaddr_maxaddr - sz - guard_sz,
+	    align, offset);
+
 	/* Quick fail if the allocation won't fit. */
-	if (uaddr->uaddr_maxaddr - uaddr->uaddr_minaddr < sz + guard_sz)
+	if (minaddr >= maxaddr)
 		return ENOMEM;
 
 	/* Select a hint. */
 	if (hint == 0)
-		hint = uvm_map_hint(vm, prot);
+		hint = uvm_map_hint(vm, prot, minaddr, maxaddr);
 	/* Clamp hint to uaddr range. */
-	hint = MIN(MAX(hint, uaddr->uaddr_minaddr),
-	    uaddr->uaddr_maxaddr - sz - guard_sz);
+	hint = MIN(MAX(hint, minaddr), maxaddr);
 
 	/* Align hint to align,offset parameters. */
 	tmp = hint;
 	hint = uvm_addr_align_forward(tmp, align, offset);
 	/* Check for overflow during alignment. */
-	if (hint < tmp || hint > uaddr->uaddr_maxaddr - sz - guard_sz)
+	if (hint < tmp || hint > maxaddr)
 		return ENOMEM; /* Compatibility mode: never look backwards. */
 
 	before_gap = 0;
diff --git a/sys/uvm/uvm_map.c b/sys/uvm/uvm_map.c
index 2323189738f..80bfee3bb13 100644
--- a/sys/uvm/uvm_map.c
+++ b/sys/uvm/uvm_map.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.c,v 1.188 2015/03/14 03:38:53 jsg Exp $	*/
+/*	$OpenBSD: uvm_map.c,v 1.189 2015/03/30 21:08:40 miod Exp $	*/
 /*	$NetBSD: uvm_map.c,v 1.86 2000/11/27 08:40:03 chs Exp $	*/
 
 /*
@@ -3713,7 +3713,8 @@ uvmspace_fork(struct process *pr)
  * creating a new mapping with "prot" protection.
  */
 vaddr_t
-uvm_map_hint(struct vmspace *vm, vm_prot_t prot)
+uvm_map_hint(struct vmspace *vm, vm_prot_t prot, vaddr_t minaddr,
+    vaddr_t maxaddr)
 {
 	vaddr_t addr;
 	vaddr_t spacing;
@@ -3746,6 +3747,10 @@ uvm_map_hint(struct vmspace *vm, vm_prot_t prot)
 	if (vm->vm_dused < spacing >> PAGE_SHIFT)
 		addr += BRKSIZ;
 #if !defined(__vax__)
+	if (addr < maxaddr) {
+		while (spacing > maxaddr - addr)
+			spacing >>= 1;
+	}
 	addr += arc4random() & spacing;
 #endif
 	return (round_page(addr));
diff --git a/sys/uvm/uvm_map.h b/sys/uvm/uvm_map.h
index df132b17459..c23e070f703 100644
--- a/sys/uvm/uvm_map.h
+++ b/sys/uvm/uvm_map.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.h,v 1.53 2015/02/06 09:04:34 tedu Exp $	*/
+/*	$OpenBSD: uvm_map.h,v 1.54 2015/03/30 21:08:40 miod Exp $	*/
 /*	$NetBSD: uvm_map.h,v 1.24 2001/02/18 21:19:08 chs Exp $	*/
 
 /*
@@ -384,7 +384,7 @@ vm_map_t	uvm_map_create(pmap_t, vaddr_t, vaddr_t, int);
 int		uvm_map_extract(struct vm_map*, vaddr_t, vsize_t, vaddr_t*,
 		    int);
 vaddr_t		uvm_map_pie(vaddr_t);
-vaddr_t		uvm_map_hint(struct vmspace *, vm_prot_t);
+vaddr_t		uvm_map_hint(struct vmspace *, vm_prot_t, vaddr_t, vaddr_t);
 int		uvm_map_inherit(vm_map_t, vaddr_t, vaddr_t, vm_inherit_t);
 int		uvm_map_advice(vm_map_t, vaddr_t, vaddr_t, int);
 void		uvm_map_init(void);
diff --git a/sys/uvm/uvm_mmap.c b/sys/uvm/uvm_mmap.c
index b2d749cfb54..9f4205c8d51 100644
--- a/sys/uvm/uvm_mmap.c
+++ b/sys/uvm/uvm_mmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_mmap.c,v 1.107 2015/02/13 13:35:03 millert Exp $	*/
+/*	$OpenBSD: uvm_mmap.c,v 1.108 2015/03/30 21:08:40 miod Exp $	*/
 /*	$NetBSD: uvm_mmap.c,v 1.49 2001/02/18 21:19:08 chs Exp $	*/
 
 /*
@@ -152,7 +152,8 @@ sys_mquery(struct proc *p, void *v, register_t *retval)
 	}
 
 	if (vaddr == 0)
-		vaddr = uvm_map_hint(p->p_vmspace, prot);
+		vaddr = uvm_map_hint(p->p_vmspace, prot, VM_MIN_ADDRESS,
+		    VM_MAXUSER_ADDRESS);
 
 	error = uvm_map_mquery(&p->p_vmspace->vm_map, &vaddr, size, uoff,
 	    flags);