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 #include <linux/sched/task_stack.h>
  29
  30 #include <linux/uaccess.h>
  31 #include <asm/cacheflush.h>
  32
  33 static int load_aout_binary(struct linux_binprm *);
  34 static int load_aout_library(struct file*);
  35
  36 static struct linux_binfmt aout_format = {
  37         .module         = THIS_MODULE,
  38         .load_binary    = load_aout_binary,
  39         .load_shlib     = load_aout_library,
  40 };
  41
  42 #define BAD_ADDR(x)     ((unsigned long)(x) >= TASK_SIZE)
  43
  44 static int set_brk(unsigned long start, unsigned long end)
  45 {
  46         start = PAGE_ALIGN(start);
  47         end = PAGE_ALIGN(end);
  48         if (end > start)
  49                 return vm_brk(start, end - start);
  50         return 0;
  51 }
  52
  53 /*
  54  * create_aout_tables() parses the env- and arg-strings in new user
  55  * memory and creates the pointer tables from them, and puts their
  56  * addresses on the "stack", returning the new stack pointer value.
  57  */
  58 static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
  59 {
  60         char __user * __user *argv;
  61         char __user * __user *envp;
  62         unsigned long __user *sp;
  63         int argc = bprm->argc;
  64         int envc = bprm->envc;
  65
  66         sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
  67 #ifdef __alpha__
  68 /* whee.. test-programs are so much fun. */
  69         put_user(0, --sp);
  70         put_user(0, --sp);
  71         if (bprm->loader) {
  72                 put_user(0, --sp);
  73                 put_user(1003, --sp);
  74                 put_user(bprm->loader, --sp);
  75                 put_user(1002, --sp);
  76         }
  77         put_user(bprm->exec, --sp);
  78         put_user(1001, --sp);
  79 #endif
  80         sp -= envc+1;
  81         envp = (char __user * __user *) sp;
  82         sp -= argc+1;
  83         argv = (char __user * __user *) sp;
  84 #ifndef __alpha__
  85         put_user((unsigned long) envp,--sp);
  86         put_user((unsigned long) argv,--sp);
  87 #endif
  88         put_user(argc,--sp);
  89         current->mm->arg_start = (unsigned long) p;
  90         while (argc-->0) {
  91                 char c;
  92                 put_user(p,argv++);
  93                 do {
  94                         get_user(c,p++);
  95                 } while (c);
  96         }
  97         put_user(NULL,argv);
  98         current->mm->arg_end = current->mm->env_start = (unsigned long) p;
  99         while (envc-->0) {
 100                 char c;
 101                 put_user(p,envp++);
 102                 do {
 103                         get_user(c,p++);
 104                 } while (c);
 105         }
 106         put_user(NULL,envp);
 107         current->mm->env_end = (unsigned long) p;
 108         return sp;
 109 }
 110
 111 /*
 112  * These are the functions used to load a.out style executables and shared
 113  * libraries.  There is no binary dependent code anywhere else.
 114  */
 115
 116 static int load_aout_binary(struct linux_binprm * bprm)
 117 {
 118         struct pt_regs *regs = current_pt_regs();
 119         struct exec ex;
 120         unsigned long error;
 121         unsigned long fd_offset;
 122         unsigned long rlim;
 123         int retval;
 124
 125         ex = *((struct exec *) bprm->buf);              /* exec-header */
 126         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
 127              N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
 128             N_TRSIZE(ex) || N_DRSIZE(ex) ||
 129             i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
 130                 return -ENOEXEC;
 131         }
 132
 133         /*
 134          * Requires a mmap handler. This prevents people from using a.out
 135          * as part of an exploit attack against /proc-related vulnerabilities.
 136          */
 137         if (!bprm->file->f_op->mmap)
 138                 return -ENOEXEC;
 139
 140         fd_offset = N_TXTOFF(ex);
 141
 142         /* Check initial limits. This avoids letting people circumvent
 143          * size limits imposed on them by creating programs with large
 144          * arrays in the data or bss.
 145          */
 146         rlim = rlimit(RLIMIT_DATA);
 147         if (rlim >= RLIM_INFINITY)
 148                 rlim = ~0;
 149         if (ex.a_data + ex.a_bss > rlim)
 150                 return -ENOMEM;
 151
 152         /* Flush all traces of the currently running executable */
 153         retval = flush_old_exec(bprm);
 154         if (retval)
 155                 return retval;
 156
 157         /* OK, This is the point of no return */
 158 #ifdef __alpha__
 159         SET_AOUT_PERSONALITY(bprm, ex);
 160 #else
 161         set_personality(PER_LINUX);
 162 #endif
 163         setup_new_exec(bprm);
 164
 165         current->mm->end_code = ex.a_text +
 166                 (current->mm->start_code = N_TXTADDR(ex));
 167         current->mm->end_data = ex.a_data +
 168                 (current->mm->start_data = N_DATADDR(ex));
 169         current->mm->brk = ex.a_bss +
 170                 (current->mm->start_brk = N_BSSADDR(ex));
 171
 172         retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
 173         if (retval < 0)
 174                 return retval;
 175
 176         install_exec_creds(bprm);
 177
 178         if (N_MAGIC(ex) == OMAGIC) {
 179                 unsigned long text_addr, map_size;
 180                 loff_t pos;
 181
 182                 text_addr = N_TXTADDR(ex);
 183
 184 #ifdef __alpha__
 185                 pos = fd_offset;
 186                 map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
 187 #else
 188                 pos = 32;
 189                 map_size = ex.a_text+ex.a_data;
 190 #endif
 191                 error = vm_brk(text_addr & PAGE_MASK, map_size);
 192                 if (error)
 193                         return error;
 194
 195                 error = read_code(bprm->file, text_addr, pos,
 196                                   ex.a_text+ex.a_data);
 197                 if ((signed long)error < 0)
 198                         return error;
 199         } else {
 200                 if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
 201                     (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
 202                 {
 203                         printk(KERN_NOTICE "executable not page aligned\n");
 204                 }
 205
 206                 if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
 207                 {
 208                         printk(KERN_WARNING
 209                                "fd_offset is not page aligned. Please convert program: %pD\n",
 210                                bprm->file);
 211                 }
 212
 213                 if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
 214                         error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
 215                         if (error)
 216                                 return error;
 217
 218                         read_code(bprm->file, N_TXTADDR(ex), fd_offset,
 219                                   ex.a_text + ex.a_data);
 220                         goto beyond_if;
 221                 }
 222
 223                 error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
 224                         PROT_READ | PROT_EXEC,
 225                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
 226                         fd_offset);
 227
 228                 if (error != N_TXTADDR(ex))
 229                         return error;
 230
 231                 error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
 232                                 PROT_READ | PROT_WRITE | PROT_EXEC,
 233                                 MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
 234                                 fd_offset + ex.a_text);
 235                 if (error != N_DATADDR(ex))
 236                         return error;
 237         }
 238 beyond_if:
 239         set_binfmt(&aout_format);
 240
 241         retval = set_brk(current->mm->start_brk, current->mm->brk);
 242         if (retval < 0)
 243                 return retval;
 244
 245         current->mm->start_stack =
 246                 (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
 247 #ifdef __alpha__
 248         regs->gp = ex.a_gpvalue;
 249 #endif
 250         finalize_exec(bprm);
 251         start_thread(regs, ex.a_entry, current->mm->start_stack);
 252         return 0;
 253 }
 254
 255 static int load_aout_library(struct file *file)
 256 {
 257         struct inode * inode;
 258         unsigned long bss, start_addr, len;
 259         unsigned long error;
 260         int retval;
 261         struct exec ex;
 262         loff_t pos = 0;
 263
 264         inode = file_inode(file);
 265
 266         retval = -ENOEXEC;
 267         error = kernel_read(file, &ex, sizeof(ex), &pos);
 268         if (error != sizeof(ex))
 269                 goto out;
 270
 271         /* We come in here for the regular a.out style of shared libraries */
 272         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
 273             N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
 274             i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
 275                 goto out;
 276         }
 277
 278         /*
 279          * Requires a mmap handler. This prevents people from using a.out
 280          * as part of an exploit attack against /proc-related vulnerabilities.
 281          */
 282         if (!file->f_op->mmap)
 283                 goto out;
 284
 285         if (N_FLAGS(ex))
 286                 goto out;
 287
 288         /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
 289            this off to get the starting address for the page */
 290
 291         start_addr =  ex.a_entry & 0xfffff000;
 292
 293         if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
 294                 if (printk_ratelimit())
 295                 {
 296                         printk(KERN_WARNING
 297                                "N_TXTOFF is not page aligned. Please convert library: %pD\n",
 298                                file);
 299                 }
 300                 retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
 301                 if (retval)
 302                         goto out;
 303
 304                 read_code(file, start_addr, N_TXTOFF(ex),
 305                           ex.a_text + ex.a_data);
 306                 retval = 0;
 307                 goto out;
 308         }
 309         /* Now use mmap to map the library into memory. */
 310         error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
 311                         PROT_READ | PROT_WRITE | PROT_EXEC,
 312                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
 313                         N_TXTOFF(ex));
 314         retval = error;
 315         if (error != start_addr)
 316                 goto out;
 317
 318         len = PAGE_ALIGN(ex.a_text + ex.a_data);
 319         bss = ex.a_text + ex.a_data + ex.a_bss;
 320         if (bss > len) {
 321                 retval = vm_brk(start_addr + len, bss - len);
 322                 if (retval)
 323                         goto out;
 324         }
 325         retval = 0;
 326 out:
 327         return retval;
 328 }
 329
 330 static int __init init_aout_binfmt(void)
 331 {
 332         register_binfmt(&aout_format);
 333         return 0;
 334 }
 335
 336 static void __exit exit_aout_binfmt(void)
 337 {
 338         unregister_binfmt(&aout_format);
 339 }
 340
 341 core_initcall(init_aout_binfmt);
 342 module_exit(exit_aout_binfmt);
 343 MODULE_LICENSE("GPL");