binfmt_aout.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/binfmt_aout.c
   4  *
   5  *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
   6  */
   7
   8 #include <linux/module.h>
   9
  10 #include <linux/time.h>
  11 #include <linux/kernel.h>
  12 #include <linux/mm.h>
  13 #include <linux/mman.h>
  14 #include <linux/a.out.h>
  15 #include <linux/errno.h>
  16 #include <linux/signal.h>
  17 #include <linux/string.h>
  18 #include <linux/fs.h>
  19 #include <linux/file.h>
  20 #include <linux/stat.h>
  21 #include <linux/fcntl.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/user.h>
  24 #include <linux/binfmts.h>
  25 #include <linux/personality.h>
  26 #include <linux/init.h>
  27 #include <linux/coredump.h>
  28 #include <linux/slab.h>
  29 #include <linux/sched/task_stack.h>
  30
  31 #include <linux/uaccess.h>
  32 #include <asm/cacheflush.h>
  33
  34 static int load_aout_binary(struct linux_binprm *);
  35 static int load_aout_library(struct file*);
  36
  37 static struct linux_binfmt aout_format = {
  38         .module         = THIS_MODULE,
  39         .load_binary    = load_aout_binary,
  40         .load_shlib     = load_aout_library,
  41 };
  42
  43 #define BAD_ADDR(x)     ((unsigned long)(x) >= TASK_SIZE)
  44
  45 static int set_brk(unsigned long start, unsigned long end)
  46 {
  47         start = PAGE_ALIGN(start);
  48         end = PAGE_ALIGN(end);
  49         if (end > start)
  50                 return vm_brk(start, end - start);
  51         return 0;
  52 }
  53
  54 /*
  55  * create_aout_tables() parses the env- and arg-strings in new user
  56  * memory and creates the pointer tables from them, and puts their
  57  * addresses on the "stack", returning the new stack pointer value.
  58  */
  59 static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
  60 {
  61         char __user * __user *argv;
  62         char __user * __user *envp;
  63         unsigned long __user *sp;
  64         int argc = bprm->argc;
  65         int envc = bprm->envc;
  66
  67         sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
  68 #ifdef __alpha__
  69 /* whee.. test-programs are so much fun. */
  70         put_user(0, --sp);
  71         put_user(0, --sp);
  72         if (bprm->loader) {
  73                 put_user(0, --sp);
  74                 put_user(1003, --sp);
  75                 put_user(bprm->loader, --sp);
  76                 put_user(1002, --sp);
  77         }
  78         put_user(bprm->exec, --sp);
  79         put_user(1001, --sp);
  80 #endif
  81         sp -= envc+1;
  82         envp = (char __user * __user *) sp;
  83         sp -= argc+1;
  84         argv = (char __user * __user *) sp;
  85 #ifndef __alpha__
  86         put_user((unsigned long) envp,--sp);
  87         put_user((unsigned long) argv,--sp);
  88 #endif
  89         put_user(argc,--sp);
  90         current->mm->arg_start = (unsigned long) p;
  91         while (argc-->0) {
  92                 char c;
  93                 put_user(p,argv++);
  94                 do {
  95                         get_user(c,p++);
  96                 } while (c);
  97         }
  98         put_user(NULL,argv);
  99         current->mm->arg_end = current->mm->env_start = (unsigned long) p;
 100         while (envc-->0) {
 101                 char c;
 102                 put_user(p,envp++);
 103                 do {
 104                         get_user(c,p++);
 105                 } while (c);
 106         }
 107         put_user(NULL,envp);
 108         current->mm->env_end = (unsigned long) p;
 109         return sp;
 110 }
 111
 112 /*
 113  * These are the functions used to load a.out style executables and shared
 114  * libraries.  There is no binary dependent code anywhere else.
 115  */
 116
 117 static int load_aout_binary(struct linux_binprm * bprm)
 118 {
 119         struct pt_regs *regs = current_pt_regs();
 120         struct exec ex;
 121         unsigned long error;
 122         unsigned long fd_offset;
 123         unsigned long rlim;
 124         int retval;
 125
 126         ex = *((struct exec *) bprm->buf);              /* exec-header */
 127         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
 128              N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
 129             N_TRSIZE(ex) || N_DRSIZE(ex) ||
 130             i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
 131                 return -ENOEXEC;
 132         }
 133
 134         /*
 135          * Requires a mmap handler. This prevents people from using a.out
 136          * as part of an exploit attack against /proc-related vulnerabilities.
 137          */
 138         if (!bprm->file->f_op->mmap)
 139                 return -ENOEXEC;
 140
 141         fd_offset = N_TXTOFF(ex);
 142
 143         /* Check initial limits. This avoids letting people circumvent
 144          * size limits imposed on them by creating programs with large
 145          * arrays in the data or bss.
 146          */
 147         rlim = rlimit(RLIMIT_DATA);
 148         if (rlim >= RLIM_INFINITY)
 149                 rlim = ~0;
 150         if (ex.a_data + ex.a_bss > rlim)
 151                 return -ENOMEM;
 152
 153         /* Flush all traces of the currently running executable */
 154         retval = flush_old_exec(bprm);
 155         if (retval)
 156                 return retval;
 157
 158         /* OK, This is the point of no return */
 159 #ifdef __alpha__
 160         SET_AOUT_PERSONALITY(bprm, ex);
 161 #else
 162         set_personality(PER_LINUX);
 163 #endif
 164         setup_new_exec(bprm);
 165
 166         current->mm->end_code = ex.a_text +
 167                 (current->mm->start_code = N_TXTADDR(ex));
 168         current->mm->end_data = ex.a_data +
 169                 (current->mm->start_data = N_DATADDR(ex));
 170         current->mm->brk = ex.a_bss +
 171                 (current->mm->start_brk = N_BSSADDR(ex));
 172
 173         retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
 174         if (retval < 0)
 175                 return retval;
 176
 177         install_exec_creds(bprm);
 178
 179         if (N_MAGIC(ex) == OMAGIC) {
 180                 unsigned long text_addr, map_size;
 181                 loff_t pos;
 182
 183                 text_addr = N_TXTADDR(ex);
 184
 185 #ifdef __alpha__
 186                 pos = fd_offset;
 187                 map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
 188 #else
 189                 pos = 32;
 190                 map_size = ex.a_text+ex.a_data;
 191 #endif
 192                 error = vm_brk(text_addr & PAGE_MASK, map_size);
 193                 if (error)
 194                         return error;
 195
 196                 error = read_code(bprm->file, text_addr, pos,
 197                                   ex.a_text+ex.a_data);
 198                 if ((signed long)error < 0)
 199                         return error;
 200         } else {
 201                 if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
 202                     (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
 203                 {
 204                         printk(KERN_NOTICE "executable not page aligned\n");
 205                 }
 206
 207                 if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
 208                 {
 209                         printk(KERN_WARNING
 210                                "fd_offset is not page aligned. Please convert program: %pD\n",
 211                                bprm->file);
 212                 }
 213
 214                 if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
 215                         error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
 216                         if (error)
 217                                 return error;
 218
 219                         read_code(bprm->file, N_TXTADDR(ex), fd_offset,
 220                                   ex.a_text + ex.a_data);
 221                         goto beyond_if;
 222                 }
 223
 224                 error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
 225                         PROT_READ | PROT_EXEC,
 226                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
 227                         fd_offset);
 228
 229                 if (error != N_TXTADDR(ex))
 230                         return error;
 231
 232                 error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
 233                                 PROT_READ | PROT_WRITE | PROT_EXEC,
 234                                 MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
 235                                 fd_offset + ex.a_text);
 236                 if (error != N_DATADDR(ex))
 237                         return error;
 238         }
 239 beyond_if:
 240         set_binfmt(&aout_format);
 241
 242         retval = set_brk(current->mm->start_brk, current->mm->brk);
 243         if (retval < 0)
 244                 return retval;
 245
 246         current->mm->start_stack =
 247                 (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
 248 #ifdef __alpha__
 249         regs->gp = ex.a_gpvalue;
 250 #endif
 251         finalize_exec(bprm);
 252         start_thread(regs, ex.a_entry, current->mm->start_stack);
 253         return 0;
 254 }
 255
 256 static int load_aout_library(struct file *file)
 257 {
 258         struct inode * inode;
 259         unsigned long bss, start_addr, len;
 260         unsigned long error;
 261         int retval;
 262         struct exec ex;
 263         loff_t pos = 0;
 264
 265         inode = file_inode(file);
 266
 267         retval = -ENOEXEC;
 268         error = kernel_read(file, &ex, sizeof(ex), &pos);
 269         if (error != sizeof(ex))
 270                 goto out;
 271
 272         /* We come in here for the regular a.out style of shared libraries */
 273         if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
 274             N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
 275             i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
 276                 goto out;
 277         }
 278
 279         /*
 280          * Requires a mmap handler. This prevents people from using a.out
 281          * as part of an exploit attack against /proc-related vulnerabilities.
 282          */
 283         if (!file->f_op->mmap)
 284                 goto out;
 285
 286         if (N_FLAGS(ex))
 287                 goto out;
 288
 289         /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
 290            this off to get the starting address for the page */
 291
 292         start_addr =  ex.a_entry & 0xfffff000;
 293
 294         if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
 295                 if (printk_ratelimit())
 296                 {
 297                         printk(KERN_WARNING
 298                                "N_TXTOFF is not page aligned. Please convert library: %pD\n",
 299                                file);
 300                 }
 301                 retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
 302                 if (retval)
 303                         goto out;
 304
 305                 read_code(file, start_addr, N_TXTOFF(ex),
 306                           ex.a_text + ex.a_data);
 307                 retval = 0;
 308                 goto out;
 309         }
 310         /* Now use mmap to map the library into memory. */
 311         error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
 312                         PROT_READ | PROT_WRITE | PROT_EXEC,
 313                         MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
 314                         N_TXTOFF(ex));
 315         retval = error;
 316         if (error != start_addr)
 317                 goto out;
 318
 319         len = PAGE_ALIGN(ex.a_text + ex.a_data);
 320         bss = ex.a_text + ex.a_data + ex.a_bss;
 321         if (bss > len) {
 322                 retval = vm_brk(start_addr + len, bss - len);
 323                 if (retval)
 324                         goto out;
 325         }
 326         retval = 0;
 327 out:
 328         return retval;
 329 }
 330
 331 static int __init init_aout_binfmt(void)
 332 {
 333         register_binfmt(&aout_format);
 334         return 0;
 335 }
 336
 337 static void __exit exit_aout_binfmt(void)
 338 {
 339         unregister_binfmt(&aout_format);
 340 }
 341
 342 core_initcall(init_aout_binfmt);
 343 module_exit(exit_aout_binfmt);
 344 MODULE_LICENSE("GPL");