/*- * Copyright (c) 2005, Bosko Milekic . * 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 __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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data"); /* * The vm_memguard_divisor variable controls how much of kmem_map should be * reserved for MemGuard. */ static u_int vm_memguard_divisor; SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN, &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 vm_offset_t memguard_cursor; 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_wrap; static u_long memguard_succ; static u_long memguard_fail_kva; static u_long memguard_fail_pgs; SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD, &memguard_cursor, 0, "MemGuard cursor"); 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, wrapcnt, CTLFLAG_RD, &memguard_wrap, 0, "MemGuard cursor wrap count"); 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; TUNABLE_INT("vm.memguard.options", &memguard_options); SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RW, &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; TUNABLE_INT("vm.memguard.frequency", &memguard_frequency); SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RW, &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 kmem_map. The memguard memory will be a submap. */ unsigned long memguard_fudge(unsigned long km_size, const struct vm_map *parent_map) { u_long mem_pgs, parent_size; vm_memguard_divisor = 10; 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 = 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 VM map (contiguous chunk of address space). */ 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_cursor = base; 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"); #if 0 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD, &memguard_map->size, "MemGuard KVA used"); #endif } 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(p->wire_count != 0 && p->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(p->wire_count != 0 && p->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; u_long size_p, size_v; int do_guard, 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. We will only actually add a * vm_map_entry and get pages for the original request. Save * the value of memguard_options so we have a consistent * value. */ 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 * uma_large_alloc(), 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; } /* * Keep a moving cursor so we don't recycle KVA as long as * possible. It's not perfect, since we don't know in what * order previous allocations will be free'd, but it's simple * and fast, and requires O(1) additional storage if guard * pages are not used. * * XXX This scheme will lead to greater fragmentation of the * map, unless vm_map_findspace() is tweaked. */ for (;;) { if (vmem_xalloc(memguard_arena, size_v, 0, 0, 0, memguard_cursor, VMEM_ADDR_MAX, M_BESTFIT | M_NOWAIT, &addr) == 0) break; /* * The map has no space. This may be due to * fragmentation, or because the cursor is near the * end of the map. */ if (memguard_cursor == memguard_base) { memguard_fail_kva++; addr = (vm_offset_t)NULL; goto out; } memguard_wrap++; memguard_cursor = memguard_base; } if (do_guard) addr += PAGE_SIZE; rv = kmem_back(kmem_object, addr, size_p, flags); if (rv != KERN_SUCCESS) { vmem_xfree(memguard_arena, addr, size_v); memguard_fail_pgs++; addr = (vm_offset_t)NULL; goto out; } memguard_cursor = addr + size_v; *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(kmem_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 comparsion 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 comparsion is to always compare zone name, * but it is also the slowest way. */ return (strcmp(zone->uz_name, vm_memguard_desc) == 0); }