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