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Linux/fs/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 *);
 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                 unsigned long addr;
132                 addr = vm_brk(start, end - start);
133                 if (BAD_ADDR(addr))
134                         return addr;
135         }
136         return 0;
137 }
138 
139 /*
140  * create_aout_tables() parses the env- and arg-strings in new user
141  * memory and creates the pointer tables from them, and puts their
142  * addresses on the "stack", returning the new stack pointer value.
143  */
144 static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
145 {
146         char __user * __user *argv;
147         char __user * __user *envp;
148         unsigned long __user *sp;
149         int argc = bprm->argc;
150         int envc = bprm->envc;
151 
152         sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
153 #ifdef __alpha__
154 /* whee.. test-programs are so much fun. */
155         put_user(0, --sp);
156         put_user(0, --sp);
157         if (bprm->loader) {
158                 put_user(0, --sp);
159                 put_user(1003, --sp);
160                 put_user(bprm->loader, --sp);
161                 put_user(1002, --sp);
162         }
163         put_user(bprm->exec, --sp);
164         put_user(1001, --sp);
165 #endif
166         sp -= envc+1;
167         envp = (char __user * __user *) sp;
168         sp -= argc+1;
169         argv = (char __user * __user *) sp;
170 #ifndef __alpha__
171         put_user((unsigned long) envp,--sp);
172         put_user((unsigned long) argv,--sp);
173 #endif
174         put_user(argc,--sp);
175         current->mm->arg_start = (unsigned long) p;
176         while (argc-->0) {
177                 char c;
178                 put_user(p,argv++);
179                 do {
180                         get_user(c,p++);
181                 } while (c);
182         }
183         put_user(NULL,argv);
184         current->mm->arg_end = current->mm->env_start = (unsigned long) p;
185         while (envc-->0) {
186                 char c;
187                 put_user(p,envp++);
188                 do {
189                         get_user(c,p++);
190                 } while (c);
191         }
192         put_user(NULL,envp);
193         current->mm->env_end = (unsigned long) p;
194         return sp;
195 }
196 
197 /*
198  * These are the functions used to load a.out style executables and shared
199  * libraries.  There is no binary dependent code anywhere else.
200  */
201 
202 static int load_aout_binary(struct linux_binprm * bprm)
203 {
204         struct pt_regs *regs = current_pt_regs();
205         struct exec ex;
206         unsigned long error;
207         unsigned long fd_offset;
208         unsigned long rlim;
209         int retval;
210 
211         ex = *((struct exec *) bprm->buf);              /* exec-header */
212         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
213              N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
214             N_TRSIZE(ex) || N_DRSIZE(ex) ||
215             i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
216                 return -ENOEXEC;
217         }
218 
219         /*
220          * Requires a mmap handler. This prevents people from using a.out
221          * as part of an exploit attack against /proc-related vulnerabilities.
222          */
223         if (!bprm->file->f_op->mmap)
224                 return -ENOEXEC;
225 
226         fd_offset = N_TXTOFF(ex);
227 
228         /* Check initial limits. This avoids letting people circumvent
229          * size limits imposed on them by creating programs with large
230          * arrays in the data or bss.
231          */
232         rlim = rlimit(RLIMIT_DATA);
233         if (rlim >= RLIM_INFINITY)
234                 rlim = ~0;
235         if (ex.a_data + ex.a_bss > rlim)
236                 return -ENOMEM;
237 
238         /* Flush all traces of the currently running executable */
239         retval = flush_old_exec(bprm);
240         if (retval)
241                 return retval;
242 
243         /* OK, This is the point of no return */
244 #ifdef __alpha__
245         SET_AOUT_PERSONALITY(bprm, ex);
246 #else
247         set_personality(PER_LINUX);
248 #endif
249         setup_new_exec(bprm);
250 
251         current->mm->end_code = ex.a_text +
252                 (current->mm->start_code = N_TXTADDR(ex));
253         current->mm->end_data = ex.a_data +
254                 (current->mm->start_data = N_DATADDR(ex));
255         current->mm->brk = ex.a_bss +
256                 (current->mm->start_brk = N_BSSADDR(ex));
257 
258         retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
259         if (retval < 0)
260                 return retval;
261 
262         install_exec_creds(bprm);
263 
264         if (N_MAGIC(ex) == OMAGIC) {
265                 unsigned long text_addr, map_size;
266                 loff_t pos;
267 
268                 text_addr = N_TXTADDR(ex);
269 
270 #ifdef __alpha__
271                 pos = fd_offset;
272                 map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
273 #else
274                 pos = 32;
275                 map_size = ex.a_text+ex.a_data;
276 #endif
277                 error = vm_brk(text_addr & PAGE_MASK, map_size);
278                 if (error != (text_addr & PAGE_MASK))
279                         return error;
280 
281                 error = read_code(bprm->file, text_addr, pos,
282                                   ex.a_text+ex.a_data);
283                 if ((signed long)error < 0)
284                         return error;
285         } else {
286                 if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
287                     (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
288                 {
289                         printk(KERN_NOTICE "executable not page aligned\n");
290                 }
291 
292                 if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
293                 {
294                         printk(KERN_WARNING 
295                                "fd_offset is not page aligned. Please convert program: %s\n",
296                                bprm->file->f_path.dentry->d_name.name);
297                 }
298 
299                 if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
300                         vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
301                         read_code(bprm->file, N_TXTADDR(ex), fd_offset,
302                                   ex.a_text + ex.a_data);
303                         goto beyond_if;
304                 }
305 
306                 error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
307                         PROT_READ | PROT_EXEC,
308                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
309                         fd_offset);
310 
311                 if (error != N_TXTADDR(ex))
312                         return error;
313 
314                 error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
315                                 PROT_READ | PROT_WRITE | PROT_EXEC,
316                                 MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
317                                 fd_offset + ex.a_text);
318                 if (error != N_DATADDR(ex))
319                         return error;
320         }
321 beyond_if:
322         set_binfmt(&aout_format);
323 
324         retval = set_brk(current->mm->start_brk, current->mm->brk);
325         if (retval < 0)
326                 return retval;
327 
328         current->mm->start_stack =
329                 (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
330 #ifdef __alpha__
331         regs->gp = ex.a_gpvalue;
332 #endif
333         start_thread(regs, ex.a_entry, current->mm->start_stack);
334         return 0;
335 }
336 
337 static int load_aout_library(struct file *file)
338 {
339         struct inode * inode;
340         unsigned long bss, start_addr, len;
341         unsigned long error;
342         int retval;
343         struct exec ex;
344 
345         inode = file_inode(file);
346 
347         retval = -ENOEXEC;
348         error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
349         if (error != sizeof(ex))
350                 goto out;
351 
352         /* We come in here for the regular a.out style of shared libraries */
353         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
354             N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
355             i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
356                 goto out;
357         }
358 
359         /*
360          * Requires a mmap handler. This prevents people from using a.out
361          * as part of an exploit attack against /proc-related vulnerabilities.
362          */
363         if (!file->f_op->mmap)
364                 goto out;
365 
366         if (N_FLAGS(ex))
367                 goto out;
368 
369         /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
370            this off to get the starting address for the page */
371 
372         start_addr =  ex.a_entry & 0xfffff000;
373 
374         if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
375                 if (printk_ratelimit())
376                 {
377                         printk(KERN_WARNING 
378                                "N_TXTOFF is not page aligned. Please convert library: %s\n",
379                                file->f_path.dentry->d_name.name);
380                 }
381                 vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
382                 
383                 read_code(file, start_addr, N_TXTOFF(ex),
384                           ex.a_text + ex.a_data);
385                 retval = 0;
386                 goto out;
387         }
388         /* Now use mmap to map the library into memory. */
389         error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
390                         PROT_READ | PROT_WRITE | PROT_EXEC,
391                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
392                         N_TXTOFF(ex));
393         retval = error;
394         if (error != start_addr)
395                 goto out;
396 
397         len = PAGE_ALIGN(ex.a_text + ex.a_data);
398         bss = ex.a_text + ex.a_data + ex.a_bss;
399         if (bss > len) {
400                 error = vm_brk(start_addr + len, bss - len);
401                 retval = error;
402                 if (error != start_addr + len)
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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