7fae6a1116
an unused pageq queue reference in the page structure to stash a pointer to the MemGuard FIFO. Using the page->object field caused problems because when vm_map_protect() was called the second time to set VM_PROT_DEFAULT back onto a set of pages in memguard_map, the protection in the VM would be changed but the PMAP code would lazily not restore the PG_RW bit on the underlying pages right away (see pmap_protect()). So when a page fault finally occured and the VM noticed the faulting address corresponds to a page that _does_ have write access now, it would then call into PMAP to set back PG_RW (i386 case being discussed here). However, before it got to do that, an assertion on the object lock not being owned would get triggered, as the object of the faulting page would need to be locked but was overloaded by MemGuard. This is precisely why MemGuard cannot overload page->object. Submitted by: Alan Cox (alc@)
316 lines
9.4 KiB
C
316 lines
9.4 KiB
C
/*
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* Copyright (c) 2005,
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* Bosko Milekic <bmilekic@freebsd.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* MemGuard is a simple replacement allocator for debugging only
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* which provides ElectricFence-style memory barrier protection on
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* objects being allocated, and is used to detect tampering-after-free
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* scenarios.
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*
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* See the memguard(9) man page for more information on using MemGuard.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/types.h>
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#include <sys/queue.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/malloc.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/vm_page.h>
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#include <vm/vm_map.h>
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#include <vm/vm_extern.h>
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#include <vm/memguard.h>
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/*
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* The maximum number of pages allowed per allocation. If you're using
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* MemGuard to override very large items (> MAX_PAGES_PER_ITEM in size),
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* you need to increase MAX_PAGES_PER_ITEM.
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*/
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#define MAX_PAGES_PER_ITEM 64
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/*
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* Global MemGuard data.
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*/
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static vm_map_t memguard_map;
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static unsigned long memguard_mapsize;
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static unsigned long memguard_mapused;
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struct memguard_entry {
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STAILQ_ENTRY(memguard_entry) entries;
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void *ptr;
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};
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static struct memguard_fifo {
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struct memguard_entry *stqh_first;
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struct memguard_entry **stqh_last;
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int index;
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} memguard_fifo_pool[MAX_PAGES_PER_ITEM];
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/*
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* Local prototypes.
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*/
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static void memguard_guard(void *addr, int numpgs);
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static void memguard_unguard(void *addr, int numpgs);
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static struct memguard_fifo *vtomgfifo(vm_offset_t va);
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static void vsetmgfifo(vm_offset_t va, struct memguard_fifo *mgfifo);
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static void vclrmgfifo(vm_offset_t va);
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/*
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* Local macros. MemGuard data is global, so replace these with whatever
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* your system uses to protect global data (if it is kernel-level
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* parallelized). This is for porting among BSDs.
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*/
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#define MEMGUARD_CRIT_SECTION_DECLARE static struct mtx memguard_mtx
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#define MEMGUARD_CRIT_SECTION_INIT \
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mtx_init(&memguard_mtx, "MemGuard mtx", NULL, MTX_DEF)
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#define MEMGUARD_CRIT_SECTION_ENTER mtx_lock(&memguard_mtx)
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#define MEMGUARD_CRIT_SECTION_EXIT mtx_unlock(&memguard_mtx)
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MEMGUARD_CRIT_SECTION_DECLARE;
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/*
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* Initialize the MemGuard mock allocator. All objects from MemGuard come
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* out of a single VM map (contiguous chunk of address space).
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*/
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void
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memguard_init(vm_map_t parent_map, unsigned long size)
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{
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char *base, *limit;
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int i;
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/* size must be multiple of PAGE_SIZE */
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size /= PAGE_SIZE;
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size++;
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size *= PAGE_SIZE;
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memguard_map = kmem_suballoc(parent_map, (vm_offset_t *)&base,
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(vm_offset_t *)&limit, (vm_size_t)size);
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memguard_map->system_map = 1;
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memguard_mapsize = size;
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memguard_mapused = 0;
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MEMGUARD_CRIT_SECTION_INIT;
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MEMGUARD_CRIT_SECTION_ENTER;
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for (i = 0; i < MAX_PAGES_PER_ITEM; i++) {
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STAILQ_INIT(&memguard_fifo_pool[i]);
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memguard_fifo_pool[i].index = i;
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}
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MEMGUARD_CRIT_SECTION_EXIT;
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printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
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printf("\tMEMGUARD map base: %p\n", base);
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printf("\tMEMGUARD map limit: %p\n", limit);
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printf("\tMEMGUARD map size: %ld (Bytes)\n", size);
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}
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/*
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* Allocate a single object of specified size with specified flags (either
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* M_WAITOK or M_NOWAIT).
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*/
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void *
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memguard_alloc(unsigned long size, int flags)
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{
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void *obj;
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struct memguard_entry *e = NULL;
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int numpgs;
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numpgs = size / PAGE_SIZE;
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if ((size % PAGE_SIZE) != 0)
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numpgs++;
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if (numpgs > MAX_PAGES_PER_ITEM)
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panic("MEMGUARD: You must increase MAX_PAGES_PER_ITEM " \
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"in memguard.c (requested: %d pages)", numpgs);
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if (numpgs == 0)
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return NULL;
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/*
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* If we haven't exhausted the memguard_map yet, allocate from
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* it and grab a new page, even if we have recycled pages in our
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* FIFO. This is because we wish to allow recycled pages to live
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* guarded in the FIFO for as long as possible in order to catch
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* even very late tamper-after-frees, even though it means that
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* we end up wasting more memory, this is only a DEBUGGING allocator
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* after all.
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*/
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MEMGUARD_CRIT_SECTION_ENTER;
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if (memguard_mapused >= memguard_mapsize) {
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e = STAILQ_FIRST(&memguard_fifo_pool[numpgs - 1]);
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if (e != NULL) {
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STAILQ_REMOVE(&memguard_fifo_pool[numpgs - 1], e,
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memguard_entry, entries);
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MEMGUARD_CRIT_SECTION_EXIT;
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obj = e->ptr;
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free(e, M_TEMP);
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memguard_unguard(obj, numpgs);
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if (flags & M_ZERO)
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bzero(obj, PAGE_SIZE * numpgs);
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return obj;
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}
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MEMGUARD_CRIT_SECTION_EXIT;
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if (flags & M_WAITOK)
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panic("MEMGUARD: Failed with M_WAITOK: " \
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"memguard_map too small");
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return NULL;
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}
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memguard_mapused += (PAGE_SIZE * numpgs);
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MEMGUARD_CRIT_SECTION_EXIT;
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obj = (void *)kmem_malloc(memguard_map, PAGE_SIZE * numpgs, flags);
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if (obj != NULL) {
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vsetmgfifo((vm_offset_t)obj, &memguard_fifo_pool[numpgs - 1]);
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if (flags & M_ZERO)
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bzero(obj, PAGE_SIZE * numpgs);
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} else {
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MEMGUARD_CRIT_SECTION_ENTER;
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memguard_mapused -= (PAGE_SIZE * numpgs);
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MEMGUARD_CRIT_SECTION_EXIT;
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}
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return obj;
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}
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/*
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* Free specified single object.
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*/
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void
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memguard_free(void *addr)
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{
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struct memguard_entry *e;
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struct memguard_fifo *mgfifo;
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int idx;
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int *temp;
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addr = (void *)trunc_page((unsigned long)addr);
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/*
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* Page should not be guarded by now, so force a write.
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* The purpose of this is to increase the likelihood of catching a
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* double-free, but not necessarily a tamper-after-free (the second
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* thread freeing might not write before freeing, so this forces it
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* to and, subsequently, trigger a fault).
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*/
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temp = (int *)((unsigned long)addr + (PAGE_SIZE/2)); /* in page */
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*temp = 0xd34dc0d3;
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mgfifo = vtomgfifo((vm_offset_t)addr);
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idx = mgfifo->index;
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memguard_guard(addr, idx + 1);
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e = malloc(sizeof(struct memguard_entry), M_TEMP, M_NOWAIT);
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if (e == NULL) {
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MEMGUARD_CRIT_SECTION_ENTER;
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memguard_mapused -= (PAGE_SIZE * (idx + 1));
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MEMGUARD_CRIT_SECTION_EXIT;
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memguard_unguard(addr, idx + 1); /* just in case */
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vclrmgfifo((vm_offset_t)addr);
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kmem_free(memguard_map, (vm_offset_t)addr,
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PAGE_SIZE * (idx + 1));
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return;
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}
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e->ptr = addr;
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MEMGUARD_CRIT_SECTION_ENTER;
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STAILQ_INSERT_TAIL(mgfifo, e, entries);
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MEMGUARD_CRIT_SECTION_EXIT;
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}
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/*
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* Guard a page containing specified object (make it read-only so that
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* future writes to it fail).
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*/
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static void
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memguard_guard(void *addr, int numpgs)
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{
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void *a = (void *)trunc_page((unsigned long)addr);
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if (vm_map_protect(memguard_map, (vm_offset_t)a,
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(vm_offset_t)((unsigned long)a + (PAGE_SIZE * numpgs)),
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VM_PROT_READ, FALSE) != KERN_SUCCESS)
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panic("MEMGUARD: Unable to guard page!");
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}
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/*
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* Unguard a page containing specified object (make it read-and-write to
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* allow full data access).
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*/
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static void
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memguard_unguard(void *addr, int numpgs)
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{
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void *a = (void *)trunc_page((unsigned long)addr);
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if (vm_map_protect(memguard_map, (vm_offset_t)a,
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(vm_offset_t)((unsigned long)a + (PAGE_SIZE * numpgs)),
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VM_PROT_DEFAULT, FALSE) != KERN_SUCCESS)
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panic("MEMGUARD: Unable to unguard page!");
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}
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/*
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* vtomgfifo() converts a virtual address of the first page allocated for
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* an item to a memguard_fifo_pool reference for the corresponding item's
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* size.
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*
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* vsetmgfifo() sets a reference in an underlying page for the specified
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* virtual address to an appropriate memguard_fifo_pool.
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*
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* These routines are very similar to those defined by UMA in uma_int.h.
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* The difference is that these routines store the mgfifo in one of the
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* page's fields that is unused when the page is wired rather than the
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* object field, which is used.
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*/
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static struct memguard_fifo *
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vtomgfifo(vm_offset_t va)
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{
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vm_page_t p;
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struct memguard_fifo *mgfifo;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
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("MEMGUARD: Expected wired page in vtomgfifo!"));
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mgfifo = (struct memguard_fifo *)p->pageq.tqe_next;
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return mgfifo;
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}
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static void
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vsetmgfifo(vm_offset_t va, struct memguard_fifo *mgfifo)
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{
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vm_page_t p;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
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("MEMGUARD: Expected wired page in vsetmgfifo!"));
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p->pageq.tqe_next = (vm_page_t)mgfifo;
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}
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static void vclrmgfifo(vm_offset_t va)
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{
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vm_page_t p;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
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("MEMGUARD: Expected wired page in vclrmgfifo!"));
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p->pageq.tqe_next = NULL;
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}
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