Root/fs/binfmt_aout.c

1/*
2 * linux/fs/binfmt_aout.c
3 *
4 * Copyright (C) 1991, 1992, 1996 Linus Torvalds
5 */
6
7#include <linux/module.h>
8
9#include <linux/time.h>
10#include <linux/kernel.h>
11#include <linux/mm.h>
12#include <linux/mman.h>
13#include <linux/a.out.h>
14#include <linux/errno.h>
15#include <linux/signal.h>
16#include <linux/string.h>
17#include <linux/fs.h>
18#include <linux/file.h>
19#include <linux/stat.h>
20#include <linux/fcntl.h>
21#include <linux/ptrace.h>
22#include <linux/user.h>
23#include <linux/binfmts.h>
24#include <linux/personality.h>
25#include <linux/init.h>
26#include <linux/coredump.h>
27#include <linux/slab.h>
28
29#include <asm/system.h>
30#include <asm/uaccess.h>
31#include <asm/cacheflush.h>
32#include <asm/a.out-core.h>
33
34static int load_aout_binary(struct linux_binprm *, struct pt_regs * regs);
35static int load_aout_library(struct file*);
36static int aout_core_dump(struct coredump_params *cprm);
37
38static struct linux_binfmt aout_format = {
39    .module = THIS_MODULE,
40    .load_binary = load_aout_binary,
41    .load_shlib = load_aout_library,
42    .core_dump = aout_core_dump,
43    .min_coredump = PAGE_SIZE
44};
45
46#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
47
48static int set_brk(unsigned long start, unsigned long end)
49{
50    start = PAGE_ALIGN(start);
51    end = PAGE_ALIGN(end);
52    if (end > start) {
53        unsigned long addr;
54        down_write(&current->mm->mmap_sem);
55        addr = do_brk(start, end - start);
56        up_write(&current->mm->mmap_sem);
57        if (BAD_ADDR(addr))
58            return addr;
59    }
60    return 0;
61}
62
63/*
64 * Routine writes a core dump image in the current directory.
65 * Currently only a stub-function.
66 *
67 * Note that setuid/setgid files won't make a core-dump if the uid/gid
68 * changed due to the set[u|g]id. It's enforced by the "current->mm->dumpable"
69 * field, which also makes sure the core-dumps won't be recursive if the
70 * dumping of the process results in another error..
71 */
72
73static int aout_core_dump(struct coredump_params *cprm)
74{
75    struct file *file = cprm->file;
76    mm_segment_t fs;
77    int has_dumped = 0;
78    void __user *dump_start;
79    int dump_size;
80    struct user dump;
81#ifdef __alpha__
82# define START_DATA(u) ((void __user *)u.start_data)
83#else
84# define START_DATA(u) ((void __user *)((u.u_tsize << PAGE_SHIFT) + \
85                 u.start_code))
86#endif
87# define START_STACK(u) ((void __user *)u.start_stack)
88
89    fs = get_fs();
90    set_fs(KERNEL_DS);
91    has_dumped = 1;
92    current->flags |= PF_DUMPCORE;
93           strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
94    dump.u_ar0 = offsetof(struct user, regs);
95    dump.signal = cprm->signr;
96    aout_dump_thread(cprm->regs, &dump);
97
98/* If the size of the dump file exceeds the rlimit, then see what would happen
99   if we wrote the stack, but not the data area. */
100    if ((dump.u_dsize + dump.u_ssize+1) * PAGE_SIZE > cprm->limit)
101        dump.u_dsize = 0;
102
103/* Make sure we have enough room to write the stack and data areas. */
104    if ((dump.u_ssize + 1) * PAGE_SIZE > cprm->limit)
105        dump.u_ssize = 0;
106
107/* make sure we actually have a data and stack area to dump */
108    set_fs(USER_DS);
109    if (!access_ok(VERIFY_READ, START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
110        dump.u_dsize = 0;
111    if (!access_ok(VERIFY_READ, START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
112        dump.u_ssize = 0;
113
114    set_fs(KERNEL_DS);
115/* struct user */
116    if (!dump_write(file, &dump, sizeof(dump)))
117        goto end_coredump;
118/* Now dump all of the user data. Include malloced stuff as well */
119    if (!dump_seek(cprm->file, PAGE_SIZE - sizeof(dump)))
120        goto end_coredump;
121/* now we start writing out the user space info */
122    set_fs(USER_DS);
123/* Dump the data area */
124    if (dump.u_dsize != 0) {
125        dump_start = START_DATA(dump);
126        dump_size = dump.u_dsize << PAGE_SHIFT;
127        if (!dump_write(file, dump_start, dump_size))
128            goto end_coredump;
129    }
130/* Now prepare to dump the stack area */
131    if (dump.u_ssize != 0) {
132        dump_start = START_STACK(dump);
133        dump_size = dump.u_ssize << PAGE_SHIFT;
134        if (!dump_write(file, dump_start, dump_size))
135            goto end_coredump;
136    }
137/* Finally dump the task struct. Not be used by gdb, but could be useful */
138    set_fs(KERNEL_DS);
139    if (!dump_write(file, current, sizeof(*current)))
140        goto end_coredump;
141end_coredump:
142    set_fs(fs);
143    return has_dumped;
144}
145
146/*
147 * create_aout_tables() parses the env- and arg-strings in new user
148 * memory and creates the pointer tables from them, and puts their
149 * addresses on the "stack", returning the new stack pointer value.
150 */
151static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
152{
153    char __user * __user *argv;
154    char __user * __user *envp;
155    unsigned long __user *sp;
156    int argc = bprm->argc;
157    int envc = bprm->envc;
158
159    sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
160#ifdef __alpha__
161/* whee.. test-programs are so much fun. */
162    put_user(0, --sp);
163    put_user(0, --sp);
164    if (bprm->loader) {
165        put_user(0, --sp);
166        put_user(1003, --sp);
167        put_user(bprm->loader, --sp);
168        put_user(1002, --sp);
169    }
170    put_user(bprm->exec, --sp);
171    put_user(1001, --sp);
172#endif
173    sp -= envc+1;
174    envp = (char __user * __user *) sp;
175    sp -= argc+1;
176    argv = (char __user * __user *) sp;
177#ifndef __alpha__
178    put_user((unsigned long) envp,--sp);
179    put_user((unsigned long) argv,--sp);
180#endif
181    put_user(argc,--sp);
182    current->mm->arg_start = (unsigned long) p;
183    while (argc-->0) {
184        char c;
185        put_user(p,argv++);
186        do {
187            get_user(c,p++);
188        } while (c);
189    }
190    put_user(NULL,argv);
191    current->mm->arg_end = current->mm->env_start = (unsigned long) p;
192    while (envc-->0) {
193        char c;
194        put_user(p,envp++);
195        do {
196            get_user(c,p++);
197        } while (c);
198    }
199    put_user(NULL,envp);
200    current->mm->env_end = (unsigned long) p;
201    return sp;
202}
203
204/*
205 * These are the functions used to load a.out style executables and shared
206 * libraries. There is no binary dependent code anywhere else.
207 */
208
209static int load_aout_binary(struct linux_binprm * bprm, struct pt_regs * regs)
210{
211    struct exec ex;
212    unsigned long error;
213    unsigned long fd_offset;
214    unsigned long rlim;
215    int retval;
216
217    ex = *((struct exec *) bprm->buf); /* exec-header */
218    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
219         N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
220        N_TRSIZE(ex) || N_DRSIZE(ex) ||
221        i_size_read(bprm->file->f_path.dentry->d_inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
222        return -ENOEXEC;
223    }
224
225    /*
226     * Requires a mmap handler. This prevents people from using a.out
227     * as part of an exploit attack against /proc-related vulnerabilities.
228     */
229    if (!bprm->file->f_op || !bprm->file->f_op->mmap)
230        return -ENOEXEC;
231
232    fd_offset = N_TXTOFF(ex);
233
234    /* Check initial limits. This avoids letting people circumvent
235     * size limits imposed on them by creating programs with large
236     * arrays in the data or bss.
237     */
238    rlim = rlimit(RLIMIT_DATA);
239    if (rlim >= RLIM_INFINITY)
240        rlim = ~0;
241    if (ex.a_data + ex.a_bss > rlim)
242        return -ENOMEM;
243
244    /* Flush all traces of the currently running executable */
245    retval = flush_old_exec(bprm);
246    if (retval)
247        return retval;
248
249    /* OK, This is the point of no return */
250#ifdef __alpha__
251    SET_AOUT_PERSONALITY(bprm, ex);
252#else
253    set_personality(PER_LINUX);
254#endif
255    setup_new_exec(bprm);
256
257    current->mm->end_code = ex.a_text +
258        (current->mm->start_code = N_TXTADDR(ex));
259    current->mm->end_data = ex.a_data +
260        (current->mm->start_data = N_DATADDR(ex));
261    current->mm->brk = ex.a_bss +
262        (current->mm->start_brk = N_BSSADDR(ex));
263    current->mm->free_area_cache = current->mm->mmap_base;
264    current->mm->cached_hole_size = 0;
265
266    install_exec_creds(bprm);
267     current->flags &= ~PF_FORKNOEXEC;
268
269    if (N_MAGIC(ex) == OMAGIC) {
270        unsigned long text_addr, map_size;
271        loff_t pos;
272
273        text_addr = N_TXTADDR(ex);
274
275#ifdef __alpha__
276        pos = fd_offset;
277        map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
278#else
279        pos = 32;
280        map_size = ex.a_text+ex.a_data;
281#endif
282        down_write(&current->mm->mmap_sem);
283        error = do_brk(text_addr & PAGE_MASK, map_size);
284        up_write(&current->mm->mmap_sem);
285        if (error != (text_addr & PAGE_MASK)) {
286            send_sig(SIGKILL, current, 0);
287            return error;
288        }
289
290        error = bprm->file->f_op->read(bprm->file,
291              (char __user *)text_addr,
292              ex.a_text+ex.a_data, &pos);
293        if ((signed long)error < 0) {
294            send_sig(SIGKILL, current, 0);
295            return error;
296        }
297             
298        flush_icache_range(text_addr, text_addr+ex.a_text+ex.a_data);
299    } else {
300        if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
301            (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
302        {
303            printk(KERN_NOTICE "executable not page aligned\n");
304        }
305
306        if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
307        {
308            printk(KERN_WARNING
309                   "fd_offset is not page aligned. Please convert program: %s\n",
310                   bprm->file->f_path.dentry->d_name.name);
311        }
312
313        if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
314            loff_t pos = fd_offset;
315            down_write(&current->mm->mmap_sem);
316            do_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
317            up_write(&current->mm->mmap_sem);
318            bprm->file->f_op->read(bprm->file,
319                    (char __user *)N_TXTADDR(ex),
320                    ex.a_text+ex.a_data, &pos);
321            flush_icache_range((unsigned long) N_TXTADDR(ex),
322                       (unsigned long) N_TXTADDR(ex) +
323                       ex.a_text+ex.a_data);
324            goto beyond_if;
325        }
326
327        down_write(&current->mm->mmap_sem);
328        error = do_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
329            PROT_READ | PROT_EXEC,
330            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
331            fd_offset);
332        up_write(&current->mm->mmap_sem);
333
334        if (error != N_TXTADDR(ex)) {
335            send_sig(SIGKILL, current, 0);
336            return error;
337        }
338
339        down_write(&current->mm->mmap_sem);
340         error = do_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
341                PROT_READ | PROT_WRITE | PROT_EXEC,
342                MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
343                fd_offset + ex.a_text);
344        up_write(&current->mm->mmap_sem);
345        if (error != N_DATADDR(ex)) {
346            send_sig(SIGKILL, current, 0);
347            return error;
348        }
349    }
350beyond_if:
351    set_binfmt(&aout_format);
352
353    retval = set_brk(current->mm->start_brk, current->mm->brk);
354    if (retval < 0) {
355        send_sig(SIGKILL, current, 0);
356        return retval;
357    }
358
359    retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
360    if (retval < 0) {
361        /* Someone check-me: is this error path enough? */
362        send_sig(SIGKILL, current, 0);
363        return retval;
364    }
365
366    current->mm->start_stack =
367        (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
368#ifdef __alpha__
369    regs->gp = ex.a_gpvalue;
370#endif
371    start_thread(regs, ex.a_entry, current->mm->start_stack);
372    return 0;
373}
374
375static int load_aout_library(struct file *file)
376{
377    struct inode * inode;
378    unsigned long bss, start_addr, len;
379    unsigned long error;
380    int retval;
381    struct exec ex;
382
383    inode = file->f_path.dentry->d_inode;
384
385    retval = -ENOEXEC;
386    error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
387    if (error != sizeof(ex))
388        goto out;
389
390    /* We come in here for the regular a.out style of shared libraries */
391    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
392        N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
393        i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
394        goto out;
395    }
396
397    /*
398     * Requires a mmap handler. This prevents people from using a.out
399     * as part of an exploit attack against /proc-related vulnerabilities.
400     */
401    if (!file->f_op || !file->f_op->mmap)
402        goto out;
403
404    if (N_FLAGS(ex))
405        goto out;
406
407    /* For QMAGIC, the starting address is 0x20 into the page. We mask
408       this off to get the starting address for the page */
409
410    start_addr = ex.a_entry & 0xfffff000;
411
412    if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
413        loff_t pos = N_TXTOFF(ex);
414
415        if (printk_ratelimit())
416        {
417            printk(KERN_WARNING
418                   "N_TXTOFF is not page aligned. Please convert library: %s\n",
419                   file->f_path.dentry->d_name.name);
420        }
421        down_write(&current->mm->mmap_sem);
422        do_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
423        up_write(&current->mm->mmap_sem);
424        
425        file->f_op->read(file, (char __user *)start_addr,
426            ex.a_text + ex.a_data, &pos);
427        flush_icache_range((unsigned long) start_addr,
428                   (unsigned long) start_addr + ex.a_text + ex.a_data);
429
430        retval = 0;
431        goto out;
432    }
433    /* Now use mmap to map the library into memory. */
434    down_write(&current->mm->mmap_sem);
435    error = do_mmap(file, start_addr, ex.a_text + ex.a_data,
436            PROT_READ | PROT_WRITE | PROT_EXEC,
437            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
438            N_TXTOFF(ex));
439    up_write(&current->mm->mmap_sem);
440    retval = error;
441    if (error != start_addr)
442        goto out;
443
444    len = PAGE_ALIGN(ex.a_text + ex.a_data);
445    bss = ex.a_text + ex.a_data + ex.a_bss;
446    if (bss > len) {
447        down_write(&current->mm->mmap_sem);
448        error = do_brk(start_addr + len, bss - len);
449        up_write(&current->mm->mmap_sem);
450        retval = error;
451        if (error != start_addr + len)
452            goto out;
453    }
454    retval = 0;
455out:
456    return retval;
457}
458
459static int __init init_aout_binfmt(void)
460{
461    return register_binfmt(&aout_format);
462}
463
464static void __exit exit_aout_binfmt(void)
465{
466    unregister_binfmt(&aout_format);
467}
468
469core_initcall(init_aout_binfmt);
470module_exit(exit_aout_binfmt);
471MODULE_LICENSE("GPL");
472

Archive Download this file



interactive