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    }
137end_coredump:
138    set_fs(fs);
139    return has_dumped;
140}
141
142/*
143 * create_aout_tables() parses the env- and arg-strings in new user
144 * memory and creates the pointer tables from them, and puts their
145 * addresses on the "stack", returning the new stack pointer value.
146 */
147static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
148{
149    char __user * __user *argv;
150    char __user * __user *envp;
151    unsigned long __user *sp;
152    int argc = bprm->argc;
153    int envc = bprm->envc;
154
155    sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
156#ifdef __alpha__
157/* whee.. test-programs are so much fun. */
158    put_user(0, --sp);
159    put_user(0, --sp);
160    if (bprm->loader) {
161        put_user(0, --sp);
162        put_user(1003, --sp);
163        put_user(bprm->loader, --sp);
164        put_user(1002, --sp);
165    }
166    put_user(bprm->exec, --sp);
167    put_user(1001, --sp);
168#endif
169    sp -= envc+1;
170    envp = (char __user * __user *) sp;
171    sp -= argc+1;
172    argv = (char __user * __user *) sp;
173#ifndef __alpha__
174    put_user((unsigned long) envp,--sp);
175    put_user((unsigned long) argv,--sp);
176#endif
177    put_user(argc,--sp);
178    current->mm->arg_start = (unsigned long) p;
179    while (argc-->0) {
180        char c;
181        put_user(p,argv++);
182        do {
183            get_user(c,p++);
184        } while (c);
185    }
186    put_user(NULL,argv);
187    current->mm->arg_end = current->mm->env_start = (unsigned long) p;
188    while (envc-->0) {
189        char c;
190        put_user(p,envp++);
191        do {
192            get_user(c,p++);
193        } while (c);
194    }
195    put_user(NULL,envp);
196    current->mm->env_end = (unsigned long) p;
197    return sp;
198}
199
200/*
201 * These are the functions used to load a.out style executables and shared
202 * libraries. There is no binary dependent code anywhere else.
203 */
204
205static int load_aout_binary(struct linux_binprm * bprm, struct pt_regs * regs)
206{
207    struct exec ex;
208    unsigned long error;
209    unsigned long fd_offset;
210    unsigned long rlim;
211    int retval;
212
213    ex = *((struct exec *) bprm->buf); /* exec-header */
214    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
215         N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
216        N_TRSIZE(ex) || N_DRSIZE(ex) ||
217        i_size_read(bprm->file->f_path.dentry->d_inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
218        return -ENOEXEC;
219    }
220
221    /*
222     * Requires a mmap handler. This prevents people from using a.out
223     * as part of an exploit attack against /proc-related vulnerabilities.
224     */
225    if (!bprm->file->f_op || !bprm->file->f_op->mmap)
226        return -ENOEXEC;
227
228    fd_offset = N_TXTOFF(ex);
229
230    /* Check initial limits. This avoids letting people circumvent
231     * size limits imposed on them by creating programs with large
232     * arrays in the data or bss.
233     */
234    rlim = rlimit(RLIMIT_DATA);
235    if (rlim >= RLIM_INFINITY)
236        rlim = ~0;
237    if (ex.a_data + ex.a_bss > rlim)
238        return -ENOMEM;
239
240    /* Flush all traces of the currently running executable */
241    retval = flush_old_exec(bprm);
242    if (retval)
243        return retval;
244
245    /* OK, This is the point of no return */
246#ifdef __alpha__
247    SET_AOUT_PERSONALITY(bprm, ex);
248#else
249    set_personality(PER_LINUX);
250#endif
251    setup_new_exec(bprm);
252
253    current->mm->end_code = ex.a_text +
254        (current->mm->start_code = N_TXTADDR(ex));
255    current->mm->end_data = ex.a_data +
256        (current->mm->start_data = N_DATADDR(ex));
257    current->mm->brk = ex.a_bss +
258        (current->mm->start_brk = N_BSSADDR(ex));
259    current->mm->free_area_cache = current->mm->mmap_base;
260    current->mm->cached_hole_size = 0;
261
262    install_exec_creds(bprm);
263     current->flags &= ~PF_FORKNOEXEC;
264
265    if (N_MAGIC(ex) == OMAGIC) {
266        unsigned long text_addr, map_size;
267        loff_t pos;
268
269        text_addr = N_TXTADDR(ex);
270
271#ifdef __alpha__
272        pos = fd_offset;
273        map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
274#else
275        pos = 32;
276        map_size = ex.a_text+ex.a_data;
277#endif
278        down_write(&current->mm->mmap_sem);
279        error = do_brk(text_addr & PAGE_MASK, map_size);
280        up_write(&current->mm->mmap_sem);
281        if (error != (text_addr & PAGE_MASK)) {
282            send_sig(SIGKILL, current, 0);
283            return error;
284        }
285
286        error = bprm->file->f_op->read(bprm->file,
287              (char __user *)text_addr,
288              ex.a_text+ex.a_data, &pos);
289        if ((signed long)error < 0) {
290            send_sig(SIGKILL, current, 0);
291            return error;
292        }
293             
294        flush_icache_range(text_addr, text_addr+ex.a_text+ex.a_data);
295    } else {
296        if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
297            (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
298        {
299            printk(KERN_NOTICE "executable not page aligned\n");
300        }
301
302        if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
303        {
304            printk(KERN_WARNING
305                   "fd_offset is not page aligned. Please convert program: %s\n",
306                   bprm->file->f_path.dentry->d_name.name);
307        }
308
309        if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
310            loff_t pos = fd_offset;
311            down_write(&current->mm->mmap_sem);
312            do_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
313            up_write(&current->mm->mmap_sem);
314            bprm->file->f_op->read(bprm->file,
315                    (char __user *)N_TXTADDR(ex),
316                    ex.a_text+ex.a_data, &pos);
317            flush_icache_range((unsigned long) N_TXTADDR(ex),
318                       (unsigned long) N_TXTADDR(ex) +
319                       ex.a_text+ex.a_data);
320            goto beyond_if;
321        }
322
323        down_write(&current->mm->mmap_sem);
324        error = do_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
325            PROT_READ | PROT_EXEC,
326            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
327            fd_offset);
328        up_write(&current->mm->mmap_sem);
329
330        if (error != N_TXTADDR(ex)) {
331            send_sig(SIGKILL, current, 0);
332            return error;
333        }
334
335        down_write(&current->mm->mmap_sem);
336         error = do_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
337                PROT_READ | PROT_WRITE | PROT_EXEC,
338                MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
339                fd_offset + ex.a_text);
340        up_write(&current->mm->mmap_sem);
341        if (error != N_DATADDR(ex)) {
342            send_sig(SIGKILL, current, 0);
343            return error;
344        }
345    }
346beyond_if:
347    set_binfmt(&aout_format);
348
349    retval = set_brk(current->mm->start_brk, current->mm->brk);
350    if (retval < 0) {
351        send_sig(SIGKILL, current, 0);
352        return retval;
353    }
354
355    retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
356    if (retval < 0) {
357        /* Someone check-me: is this error path enough? */
358        send_sig(SIGKILL, current, 0);
359        return retval;
360    }
361
362    current->mm->start_stack =
363        (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
364#ifdef __alpha__
365    regs->gp = ex.a_gpvalue;
366#endif
367    start_thread(regs, ex.a_entry, current->mm->start_stack);
368    return 0;
369}
370
371static int load_aout_library(struct file *file)
372{
373    struct inode * inode;
374    unsigned long bss, start_addr, len;
375    unsigned long error;
376    int retval;
377    struct exec ex;
378
379    inode = file->f_path.dentry->d_inode;
380
381    retval = -ENOEXEC;
382    error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
383    if (error != sizeof(ex))
384        goto out;
385
386    /* We come in here for the regular a.out style of shared libraries */
387    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
388        N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
389        i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
390        goto out;
391    }
392
393    /*
394     * Requires a mmap handler. This prevents people from using a.out
395     * as part of an exploit attack against /proc-related vulnerabilities.
396     */
397    if (!file->f_op || !file->f_op->mmap)
398        goto out;
399
400    if (N_FLAGS(ex))
401        goto out;
402
403    /* For QMAGIC, the starting address is 0x20 into the page. We mask
404       this off to get the starting address for the page */
405
406    start_addr = ex.a_entry & 0xfffff000;
407
408    if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
409        loff_t pos = N_TXTOFF(ex);
410
411        if (printk_ratelimit())
412        {
413            printk(KERN_WARNING
414                   "N_TXTOFF is not page aligned. Please convert library: %s\n",
415                   file->f_path.dentry->d_name.name);
416        }
417        down_write(&current->mm->mmap_sem);
418        do_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
419        up_write(&current->mm->mmap_sem);
420        
421        file->f_op->read(file, (char __user *)start_addr,
422            ex.a_text + ex.a_data, &pos);
423        flush_icache_range((unsigned long) start_addr,
424                   (unsigned long) start_addr + ex.a_text + ex.a_data);
425
426        retval = 0;
427        goto out;
428    }
429    /* Now use mmap to map the library into memory. */
430    down_write(&current->mm->mmap_sem);
431    error = do_mmap(file, start_addr, ex.a_text + ex.a_data,
432            PROT_READ | PROT_WRITE | PROT_EXEC,
433            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
434            N_TXTOFF(ex));
435    up_write(&current->mm->mmap_sem);
436    retval = error;
437    if (error != start_addr)
438        goto out;
439
440    len = PAGE_ALIGN(ex.a_text + ex.a_data);
441    bss = ex.a_text + ex.a_data + ex.a_bss;
442    if (bss > len) {
443        down_write(&current->mm->mmap_sem);
444        error = do_brk(start_addr + len, bss - len);
445        up_write(&current->mm->mmap_sem);
446        retval = error;
447        if (error != start_addr + len)
448            goto out;
449    }
450    retval = 0;
451out:
452    return retval;
453}
454
455static int __init init_aout_binfmt(void)
456{
457    return register_binfmt(&aout_format);
458}
459
460static void __exit exit_aout_binfmt(void)
461{
462    unregister_binfmt(&aout_format);
463}
464
465core_initcall(init_aout_binfmt);
466module_exit(exit_aout_binfmt);
467MODULE_LICENSE("GPL");
468

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