/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>.
* Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* MemGuard is a simple replacement allocator for debugging only
* which provides ElectricFence-style memory barrier protection on
* objects being allocated, and is used to detect tampering-after-free
* scenarios.
*
* See the memguard(9) man page for more information on using MemGuard.
*/
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <sys/vmem.h>
#include <sys/vmmeter.h>
#include <vm/vm.h>
#include <vm/uma.h>
#include <vm/vm_param.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/uma_int.h>
#include <vm/memguard.h>
static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
"MemGuard data");
/*
* The vm_memguard_divisor variable controls how much of kernel_arena should be
* reserved for MemGuard.
*/
static u_int vm_memguard_divisor;
SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
&vm_memguard_divisor,
0, "(kmem_size/memguard_divisor) == memguard submap size");
/*
* Short description (ks_shortdesc) of memory type to monitor.
*/
static char vm_memguard_desc[128] = "";
static struct malloc_type *vm_memguard_mtype = NULL;
TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc));
static int
memguard_sysctl_desc(SYSCTL_HANDLER_ARGS)
{
char desc[sizeof(vm_memguard_desc)];
int error;
strlcpy(desc, vm_memguard_desc, sizeof(desc));
error = sysctl_handle_string(oidp, desc, sizeof(desc), req);
if (error != 0 || req->newptr == NULL)
return (error);
mtx_lock(&malloc_mtx);
/* If mtp is NULL, it will be initialized in memguard_cmp() */
vm_memguard_mtype = malloc_desc2type(desc);
strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc));
mtx_unlock(&malloc_mtx);
return (error);
}
SYSCTL_PROC(_vm_memguard, OID_AUTO, desc,
CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
memguard_sysctl_desc, "A", "Short description of memory type to monitor");
static int
memguard_sysctl_mapused(SYSCTL_HANDLER_ARGS)
{
vmem_size_t size;
size = vmem_size(memguard_arena, VMEM_ALLOC);
return (sysctl_handle_long(oidp, &size, sizeof(size), req));
}
static vm_offset_t memguard_base;
static vm_size_t memguard_mapsize;
static vm_size_t memguard_physlimit;
static u_long memguard_wasted;
static u_long memguard_succ;
static u_long memguard_fail_kva;
static u_long memguard_fail_pgs;
SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD,
&memguard_mapsize, 0, "MemGuard private arena size");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD,
&memguard_physlimit, 0, "Limit on MemGuard memory consumption");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD,
&memguard_wasted, 0, "Excess memory used through page promotion");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD,
&memguard_succ, 0, "Count of successful MemGuard allocations");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD,
&memguard_fail_kva, 0, "MemGuard failures due to lack of KVA");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD,
&memguard_fail_pgs, 0, "MemGuard failures due to lack of pages");
#define MG_GUARD_AROUND 0x001
#define MG_GUARD_ALLLARGE 0x002
#define MG_GUARD_NOFREE 0x004
static int memguard_options = MG_GUARD_AROUND;
SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN,
&memguard_options, 0,
"MemGuard options:\n"
"\t0x001 - add guard pages around each allocation\n"
"\t0x002 - always use MemGuard for allocations over a page\n"
"\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag");
static u_int memguard_minsize;
static u_long memguard_minsize_reject;
SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW,
&memguard_minsize, 0, "Minimum size for page promotion");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD,
&memguard_minsize_reject, 0, "# times rejected for size");
static u_int memguard_frequency;
static u_long memguard_frequency_hits;
SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN,
&memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD,
&memguard_frequency_hits, 0, "# times MemGuard randomly chose");
/*
* Return a fudged value to be used for vm_kmem_size for allocating
* the kernel_arena.
*/
unsigned long
memguard_fudge(unsigned long km_size, const struct vm_map *parent_map)
{
u_long mem_pgs, parent_size;
vm_memguard_divisor = 10;
/* CTFLAG_RDTUN doesn't work during the early boot process. */
TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor);
parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) +
PAGE_SIZE;
/* Pick a conservative value if provided value sucks. */
if ((vm_memguard_divisor <= 0) ||
((parent_size / vm_memguard_divisor) == 0))
vm_memguard_divisor = 10;
/*
* Limit consumption of physical pages to
* 1/vm_memguard_divisor of system memory. If the KVA is
* smaller than this then the KVA limit comes into play first.
* This prevents memguard's page promotions from completely
* using up memory, since most malloc(9) calls are sub-page.
*/
mem_pgs = vm_cnt.v_page_count;
memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE;
/*
* We want as much KVA as we can take safely. Use at most our
* allotted fraction of the parent map's size. Limit this to
* twice the physical memory to avoid using too much memory as
* pagetable pages (size must be multiple of PAGE_SIZE).
*/
memguard_mapsize = round_page(parent_size / vm_memguard_divisor);
if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs)
memguard_mapsize = mem_pgs * 2 * PAGE_SIZE;
if (km_size + memguard_mapsize > parent_size)
memguard_mapsize = 0;
return (km_size + memguard_mapsize);
}
/*
* Initialize the MemGuard mock allocator. All objects from MemGuard come
* out of a single contiguous chunk of kernel address space that is managed
* by a vmem arena.
*/
void
memguard_init(vmem_t *parent)
{
vm_offset_t base;
vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base);
vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize,
PAGE_SIZE, 0, M_WAITOK);
memguard_base = base;
printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base);
printf("\tMEMGUARD map size: %jd KBytes\n",
(uintmax_t)memguard_mapsize >> 10);
}
/*
* Run things that can't be done as early as memguard_init().
*/
static void
memguard_sysinit(void)
{
struct sysctl_oid_list *parent;
parent = SYSCTL_STATIC_CHILDREN(_vm_memguard);
SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart",
CTLFLAG_RD, &memguard_base,
"MemGuard KVA base");
SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit",
CTLFLAG_RD, &memguard_mapsize,
"MemGuard KVA size");
SYSCTL_ADD_PROC(NULL, parent, OID_AUTO, "mapused",
CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_ULONG, NULL, 0, memguard_sysctl_mapused, "LU",
"MemGuard KVA used");
}
SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL);
/*
* v2sizep() converts a virtual address of the first page allocated for
* an item to a pointer to u_long recording the size of the original
* allocation request.
*
* This routine is very similar to those defined by UMA in uma_int.h.
* The difference is that this routine stores the originally allocated
* size in one of the page's fields that is unused when the page is
* wired rather than the object field, which is used.
*/
static u_long *
v2sizep(vm_offset_t va)
{
vm_paddr_t pa;
struct vm_page *p;
pa = pmap_kextract(va);
if (pa == 0)
panic("MemGuard detected double-free of %p", (void *)va);
p = PHYS_TO_VM_PAGE(pa);
KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE,
("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
return (&p->plinks.memguard.p);
}
static u_long *
v2sizev(vm_offset_t va)
{
vm_paddr_t pa;
struct vm_page *p;
pa = pmap_kextract(va);
if (pa == 0)
panic("MemGuard detected double-free of %p", (void *)va);
p = PHYS_TO_VM_PAGE(pa);
KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE,
("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
return (&p->plinks.memguard.v);
}
/*
* Allocate a single object of specified size with specified flags
* (either M_WAITOK or M_NOWAIT).
*/
void *
memguard_alloc(unsigned long req_size, int flags)
{
vm_offset_t addr, origaddr;
u_long size_p, size_v;
int do_guard, error, rv;
size_p = round_page(req_size);
if (size_p == 0)
return (NULL);
/*
* To ensure there are holes on both sides of the allocation,
* request 2 extra pages of KVA. Save the value of memguard_options
* so that we use a consistent value throughout this function.
*/
size_v = size_p;
do_guard = (memguard_options & MG_GUARD_AROUND) != 0;
if (do_guard)
size_v += 2 * PAGE_SIZE;
/*
* When we pass our memory limit, reject sub-page allocations.
* Page-size and larger allocations will use the same amount
* of physical memory whether we allocate or hand off to
* malloc_large(), so keep those.
*/
if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit &&
req_size < PAGE_SIZE) {
addr = (vm_offset_t)NULL;
memguard_fail_pgs++;
goto out;
}
/*
* Attempt to avoid address reuse for as long as possible, to increase
* the likelihood of catching a use-after-free.
*/
error = vmem_alloc(memguard_arena, size_v, M_NEXTFIT | M_NOWAIT,
&origaddr);
if (error != 0) {
memguard_fail_kva++;
addr = (vm_offset_t)NULL;
goto out;
}
addr = origaddr;
if (do_guard)
addr += PAGE_SIZE;
rv = kmem_back(kernel_object, addr, size_p, flags);
if (rv != KERN_SUCCESS) {
vmem_xfree(memguard_arena, origaddr, size_v);
memguard_fail_pgs++;
addr = (vm_offset_t)NULL;
goto out;
}
*v2sizep(trunc_page(addr)) = req_size;
*v2sizev(trunc_page(addr)) = size_v;
memguard_succ++;
if (req_size < PAGE_SIZE) {
memguard_wasted += (PAGE_SIZE - req_size);
if (do_guard) {
/*
* Align the request to 16 bytes, and return
* an address near the end of the page, to
* better detect array overrun.
*/
req_size = roundup2(req_size, 16);
addr += (PAGE_SIZE - req_size);
}
}
out:
return ((void *)addr);
}
int
is_memguard_addr(void *addr)
{
vm_offset_t a = (vm_offset_t)(uintptr_t)addr;
return (a >= memguard_base && a < memguard_base + memguard_mapsize);
}
/*
* Free specified single object.
*/
void
memguard_free(void *ptr)
{
vm_offset_t addr;
u_long req_size, size, sizev;
char *temp;
int i;
addr = trunc_page((uintptr_t)ptr);
req_size = *v2sizep(addr);
sizev = *v2sizev(addr);
size = round_page(req_size);
/*
* Page should not be guarded right now, so force a write.
* The purpose of this is to increase the likelihood of
* catching a double-free, but not necessarily a
* tamper-after-free (the second thread freeing might not
* write before freeing, so this forces it to and,
* subsequently, trigger a fault).
*/
temp = ptr;
for (i = 0; i < size; i += PAGE_SIZE)
temp[i] = 'M';
/*
* This requires carnal knowledge of the implementation of
* kmem_free(), but since we've already replaced kmem_malloc()
* above, it's not really any worse. We want to use the
* vm_map lock to serialize updates to memguard_wasted, since
* we had the lock at increment.
*/
kmem_unback(kernel_object, addr, size);
if (sizev > size)
addr -= PAGE_SIZE;
vmem_xfree(memguard_arena, addr, sizev);
if (req_size < PAGE_SIZE)
memguard_wasted -= (PAGE_SIZE - req_size);
}
/*
* Re-allocate an allocation that was originally guarded.
*/
void *
memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp,
int flags)
{
void *newaddr;
u_long old_size;
/*
* Allocate the new block. Force the allocation to be guarded
* as the original may have been guarded through random
* chance, and that should be preserved.
*/
if ((newaddr = memguard_alloc(size, flags)) == NULL)
return (NULL);
/* Copy over original contents. */
old_size = *v2sizep(trunc_page((uintptr_t)addr));
bcopy(addr, newaddr, min(size, old_size));
memguard_free(addr);
return (newaddr);
}
static int
memguard_cmp(unsigned long size)
{
if (size < memguard_minsize) {
memguard_minsize_reject++;
return (0);
}
if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE)
return (1);
if (memguard_frequency > 0 &&
(random() % 100000) < memguard_frequency) {
memguard_frequency_hits++;
return (1);
}
return (0);
}
int
memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size)
{
if (memguard_cmp(size))
return(1);
#if 1
/*
* The safest way of comparison is to always compare short description
* string of memory type, but it is also the slowest way.
*/
return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0);
#else
/*
* If we compare pointers, there are two possible problems:
* 1. Memory type was unloaded and new memory type was allocated at the
* same address.
* 2. Memory type was unloaded and loaded again, but allocated at a
* different address.
*/
if (vm_memguard_mtype != NULL)
return (mtp == vm_memguard_mtype);
if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) {
vm_memguard_mtype = mtp;
return (1);
}
return (0);
#endif
}
int
memguard_cmp_zone(uma_zone_t zone)
{
if ((memguard_options & MG_GUARD_NOFREE) == 0 &&
zone->uz_flags & UMA_ZONE_NOFREE)
return (0);
if (memguard_cmp(zone->uz_size))
return (1);
/*
* The safest way of comparison is to always compare zone name,
* but it is also the slowest way.
*/
return (strcmp(zone->uz_name, vm_memguard_desc) == 0);
}
unsigned long
memguard_get_req_size(const void *addr)
{
return (*v2sizep(trunc_page((uintptr_t)addr)));
}
