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Linux/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 <linux/uaccess.h>
 30 #include <asm/cacheflush.h>
 31 #include <asm/a.out-core.h>
 32 
 33 static int load_aout_binary(struct linux_binprm *);
 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         mm_segment_t fs;
 49         int has_dumped = 0;
 50         void __user *dump_start;
 51         int dump_size;
 52         struct user dump;
 53 #ifdef __alpha__
 54 #       define START_DATA(u)    ((void __user *)u.start_data)
 55 #else
 56 #       define START_DATA(u)    ((void __user *)((u.u_tsize << PAGE_SHIFT) + \
 57                                  u.start_code))
 58 #endif
 59 #       define START_STACK(u)   ((void __user *)u.start_stack)
 60 
 61         fs = get_fs();
 62         set_fs(KERNEL_DS);
 63         has_dumped = 1;
 64         strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
 65         dump.u_ar0 = offsetof(struct user, regs);
 66         dump.signal = cprm->siginfo->si_signo;
 67         aout_dump_thread(cprm->regs, &dump);
 68 
 69 /* If the size of the dump file exceeds the rlimit, then see what would happen
 70    if we wrote the stack, but not the data area.  */
 71         if ((dump.u_dsize + dump.u_ssize+1) * PAGE_SIZE > cprm->limit)
 72                 dump.u_dsize = 0;
 73 
 74 /* Make sure we have enough room to write the stack and data areas. */
 75         if ((dump.u_ssize + 1) * PAGE_SIZE > cprm->limit)
 76                 dump.u_ssize = 0;
 77 
 78 /* make sure we actually have a data and stack area to dump */
 79         set_fs(USER_DS);
 80         if (!access_ok(VERIFY_READ, START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
 81                 dump.u_dsize = 0;
 82         if (!access_ok(VERIFY_READ, START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
 83                 dump.u_ssize = 0;
 84 
 85         set_fs(KERNEL_DS);
 86 /* struct user */
 87         if (!dump_emit(cprm, &dump, sizeof(dump)))
 88                 goto end_coredump;
 89 /* Now dump all of the user data.  Include malloced stuff as well */
 90         if (!dump_skip(cprm, PAGE_SIZE - sizeof(dump)))
 91                 goto end_coredump;
 92 /* now we start writing out the user space info */
 93         set_fs(USER_DS);
 94 /* Dump the data area */
 95         if (dump.u_dsize != 0) {
 96                 dump_start = START_DATA(dump);
 97                 dump_size = dump.u_dsize << PAGE_SHIFT;
 98                 if (!dump_emit(cprm, dump_start, dump_size))
 99                         goto end_coredump;
100         }
101 /* Now prepare to dump the stack area */
102         if (dump.u_ssize != 0) {
103                 dump_start = START_STACK(dump);
104                 dump_size = dump.u_ssize << PAGE_SHIFT;
105                 if (!dump_emit(cprm, dump_start, dump_size))
106                         goto end_coredump;
107         }
108 end_coredump:
109         set_fs(fs);
110         return has_dumped;
111 }
112 #else
113 #define aout_core_dump NULL
114 #endif
115 
116 static struct linux_binfmt aout_format = {
117         .module         = THIS_MODULE,
118         .load_binary    = load_aout_binary,
119         .load_shlib     = load_aout_library,
120         .core_dump      = aout_core_dump,
121         .min_coredump   = PAGE_SIZE
122 };
123 
124 #define BAD_ADDR(x)     ((unsigned long)(x) >= TASK_SIZE)
125 
126 static int set_brk(unsigned long start, unsigned long end)
127 {
128         start = PAGE_ALIGN(start);
129         end = PAGE_ALIGN(end);
130         if (end > start)
131                 return vm_brk(start, end - start);
132         return 0;
133 }
134 
135 /*
136  * create_aout_tables() parses the env- and arg-strings in new user
137  * memory and creates the pointer tables from them, and puts their
138  * addresses on the "stack", returning the new stack pointer value.
139  */
140 static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
141 {
142         char __user * __user *argv;
143         char __user * __user *envp;
144         unsigned long __user *sp;
145         int argc = bprm->argc;
146         int envc = bprm->envc;
147 
148         sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
149 #ifdef __alpha__
150 /* whee.. test-programs are so much fun. */
151         put_user(0, --sp);
152         put_user(0, --sp);
153         if (bprm->loader) {
154                 put_user(0, --sp);
155                 put_user(1003, --sp);
156                 put_user(bprm->loader, --sp);
157                 put_user(1002, --sp);
158         }
159         put_user(bprm->exec, --sp);
160         put_user(1001, --sp);
161 #endif
162         sp -= envc+1;
163         envp = (char __user * __user *) sp;
164         sp -= argc+1;
165         argv = (char __user * __user *) sp;
166 #ifndef __alpha__
167         put_user((unsigned long) envp,--sp);
168         put_user((unsigned long) argv,--sp);
169 #endif
170         put_user(argc,--sp);
171         current->mm->arg_start = (unsigned long) p;
172         while (argc-->0) {
173                 char c;
174                 put_user(p,argv++);
175                 do {
176                         get_user(c,p++);
177                 } while (c);
178         }
179         put_user(NULL,argv);
180         current->mm->arg_end = current->mm->env_start = (unsigned long) p;
181         while (envc-->0) {
182                 char c;
183                 put_user(p,envp++);
184                 do {
185                         get_user(c,p++);
186                 } while (c);
187         }
188         put_user(NULL,envp);
189         current->mm->env_end = (unsigned long) p;
190         return sp;
191 }
192 
193 /*
194  * These are the functions used to load a.out style executables and shared
195  * libraries.  There is no binary dependent code anywhere else.
196  */
197 
198 static int load_aout_binary(struct linux_binprm * bprm)
199 {
200         struct pt_regs *regs = current_pt_regs();
201         struct exec ex;
202         unsigned long error;
203         unsigned long fd_offset;
204         unsigned long rlim;
205         int retval;
206 
207         ex = *((struct exec *) bprm->buf);              /* exec-header */
208         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
209              N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
210             N_TRSIZE(ex) || N_DRSIZE(ex) ||
211             i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
212                 return -ENOEXEC;
213         }
214 
215         /*
216          * Requires a mmap handler. This prevents people from using a.out
217          * as part of an exploit attack against /proc-related vulnerabilities.
218          */
219         if (!bprm->file->f_op->mmap)
220                 return -ENOEXEC;
221 
222         fd_offset = N_TXTOFF(ex);
223 
224         /* Check initial limits. This avoids letting people circumvent
225          * size limits imposed on them by creating programs with large
226          * arrays in the data or bss.
227          */
228         rlim = rlimit(RLIMIT_DATA);
229         if (rlim >= RLIM_INFINITY)
230                 rlim = ~0;
231         if (ex.a_data + ex.a_bss > rlim)
232                 return -ENOMEM;
233 
234         /* Flush all traces of the currently running executable */
235         retval = flush_old_exec(bprm);
236         if (retval)
237                 return retval;
238 
239         /* OK, This is the point of no return */
240 #ifdef __alpha__
241         SET_AOUT_PERSONALITY(bprm, ex);
242 #else
243         set_personality(PER_LINUX);
244 #endif
245         setup_new_exec(bprm);
246 
247         current->mm->end_code = ex.a_text +
248                 (current->mm->start_code = N_TXTADDR(ex));
249         current->mm->end_data = ex.a_data +
250                 (current->mm->start_data = N_DATADDR(ex));
251         current->mm->brk = ex.a_bss +
252                 (current->mm->start_brk = N_BSSADDR(ex));
253 
254         retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
255         if (retval < 0)
256                 return retval;
257 
258         install_exec_creds(bprm);
259 
260         if (N_MAGIC(ex) == OMAGIC) {
261                 unsigned long text_addr, map_size;
262                 loff_t pos;
263 
264                 text_addr = N_TXTADDR(ex);
265 
266 #ifdef __alpha__
267                 pos = fd_offset;
268                 map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
269 #else
270                 pos = 32;
271                 map_size = ex.a_text+ex.a_data;
272 #endif
273                 error = vm_brk(text_addr & PAGE_MASK, map_size);
274                 if (error)
275                         return error;
276 
277                 error = read_code(bprm->file, text_addr, pos,
278                                   ex.a_text+ex.a_data);
279                 if ((signed long)error < 0)
280                         return error;
281         } else {
282                 if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
283                     (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
284                 {
285                         printk(KERN_NOTICE "executable not page aligned\n");
286                 }
287 
288                 if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
289                 {
290                         printk(KERN_WARNING 
291                                "fd_offset is not page aligned. Please convert program: %pD\n",
292                                bprm->file);
293                 }
294 
295                 if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
296                         error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
297                         if (error)
298                                 return error;
299 
300                         read_code(bprm->file, N_TXTADDR(ex), fd_offset,
301                                   ex.a_text + ex.a_data);
302                         goto beyond_if;
303                 }
304 
305                 error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
306                         PROT_READ | PROT_EXEC,
307                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
308                         fd_offset);
309 
310                 if (error != N_TXTADDR(ex))
311                         return error;
312 
313                 error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
314                                 PROT_READ | PROT_WRITE | PROT_EXEC,
315                                 MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
316                                 fd_offset + ex.a_text);
317                 if (error != N_DATADDR(ex))
318                         return error;
319         }
320 beyond_if:
321         set_binfmt(&aout_format);
322 
323         retval = set_brk(current->mm->start_brk, current->mm->brk);
324         if (retval < 0)
325                 return retval;
326 
327         current->mm->start_stack =
328                 (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
329 #ifdef __alpha__
330         regs->gp = ex.a_gpvalue;
331 #endif
332         start_thread(regs, ex.a_entry, current->mm->start_stack);
333         return 0;
334 }
335 
336 static int load_aout_library(struct file *file)
337 {
338         struct inode * inode;
339         unsigned long bss, start_addr, len;
340         unsigned long error;
341         int retval;
342         struct exec ex;
343 
344         inode = file_inode(file);
345 
346         retval = -ENOEXEC;
347         error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
348         if (error != sizeof(ex))
349                 goto out;
350 
351         /* We come in here for the regular a.out style of shared libraries */
352         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
353             N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
354             i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
355                 goto out;
356         }
357 
358         /*
359          * Requires a mmap handler. This prevents people from using a.out
360          * as part of an exploit attack against /proc-related vulnerabilities.
361          */
362         if (!file->f_op->mmap)
363                 goto out;
364 
365         if (N_FLAGS(ex))
366                 goto out;
367 
368         /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
369            this off to get the starting address for the page */
370 
371         start_addr =  ex.a_entry & 0xfffff000;
372 
373         if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
374                 if (printk_ratelimit())
375                 {
376                         printk(KERN_WARNING 
377                                "N_TXTOFF is not page aligned. Please convert library: %pD\n",
378                                file);
379                 }
380                 retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
381                 if (retval)
382                         goto out;
383 
384                 read_code(file, start_addr, N_TXTOFF(ex),
385                           ex.a_text + ex.a_data);
386                 retval = 0;
387                 goto out;
388         }
389         /* Now use mmap to map the library into memory. */
390         error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
391                         PROT_READ | PROT_WRITE | PROT_EXEC,
392                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
393                         N_TXTOFF(ex));
394         retval = error;
395         if (error != start_addr)
396                 goto out;
397 
398         len = PAGE_ALIGN(ex.a_text + ex.a_data);
399         bss = ex.a_text + ex.a_data + ex.a_bss;
400         if (bss > len) {
401                 retval = vm_brk(start_addr + len, bss - len);
402                 if (retval)
403                         goto out;
404         }
405         retval = 0;
406 out:
407         return retval;
408 }
409 
410 static int __init init_aout_binfmt(void)
411 {
412         register_binfmt(&aout_format);
413         return 0;
414 }
415 
416 static void __exit exit_aout_binfmt(void)
417 {
418         unregister_binfmt(&aout_format);
419 }
420 
421 core_initcall(init_aout_binfmt);
422 module_exit(exit_aout_binfmt);
423 MODULE_LICENSE("GPL");
424 

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