LXR linux/fs/binfmt

   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
  34static int load_aout_binary(struct linux_binprm *);
  35static int load_aout_library(struct file*);
  36
  37static 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
  45static 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 */
  59static 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
 117static 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 = begin_new_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
 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, MAP_FIXED | MAP_PRIVATE,
 225                        fd_offset);
 226
 227                if (error != N_TXTADDR(ex))
 228                        return error;
 229
 230                error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
 231                                PROT_READ | PROT_WRITE | PROT_EXEC,
 232                                MAP_FIXED | MAP_PRIVATE,
 233                                fd_offset + ex.a_text);
 234                if (error != N_DATADDR(ex))
 235                        return error;
 236        }
 237beyond_if:
 238        set_binfmt(&aout_format);
 239
 240        retval = set_brk(current->mm->start_brk, current->mm->brk);
 241        if (retval < 0)
 242                return retval;
 243
 244        current->mm->start_stack =
 245                (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
 246#ifdef __alpha__
 247        regs->gp = ex.a_gpvalue;
 248#endif
 249        finalize_exec(bprm);
 250        start_thread(regs, ex.a_entry, current->mm->start_stack);
 251        return 0;
 252}
 253
 254static int load_aout_library(struct file *file)
 255{
 256        struct inode * inode;
 257        unsigned long bss, start_addr, len;
 258        unsigned long error;
 259        int retval;
 260        struct exec ex;
 261        loff_t pos = 0;
 262
 263        inode = file_inode(file);
 264
 265        retval = -ENOEXEC;
 266        error = kernel_read(file, &ex, sizeof(ex), &pos);
 267        if (error != sizeof(ex))
 268                goto out;
 269
 270        /* We come in here for the regular a.out style of shared libraries */
 271        if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
 272            N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
 273            i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
 274                goto out;
 275        }
 276
 277        /*
 278         * Requires a mmap handler. This prevents people from using a.out
 279         * as part of an exploit attack against /proc-related vulnerabilities.
 280         */
 281        if (!file->f_op->mmap)
 282                goto out;
 283
 284        if (N_FLAGS(ex))
 285                goto out;
 286
 287        /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
 288           this off to get the starting address for the page */
 289
 290        start_addr =  ex.a_entry & 0xfffff000;
 291
 292        if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
 293                if (printk_ratelimit())
 294                {
 295                        printk(KERN_WARNING 
 296                               "N_TXTOFF is not page aligned. Please convert library: %pD\n",
 297                               file);
 298                }
 299                retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
 300                if (retval)
 301                        goto out;
 302
 303                read_code(file, start_addr, N_TXTOFF(ex),
 304                          ex.a_text + ex.a_data);
 305                retval = 0;
 306                goto out;
 307        }
 308        /* Now use mmap to map the library into memory. */
 309        error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
 310                        PROT_READ | PROT_WRITE | PROT_EXEC,
 311                        MAP_FIXED | MAP_PRIVATE,
 312                        N_TXTOFF(ex));
 313        retval = error;
 314        if (error != start_addr)
 315                goto out;
 316
 317        len = PAGE_ALIGN(ex.a_text + ex.a_data);
 318        bss = ex.a_text + ex.a_data + ex.a_bss;
 319        if (bss > len) {
 320                retval = vm_brk(start_addr + len, bss - len);
 321                if (retval)
 322                        goto out;
 323        }
 324        retval = 0;
 325out:
 326        return retval;
 327}
 328
 329static int __init init_aout_binfmt(void)
 330{
 331        register_binfmt(&aout_format);
 332        return 0;
 333}
 334
 335static void __exit exit_aout_binfmt(void)
 336{
 337        unregister_binfmt(&aout_format);
 338}
 339
 340core_initcall(init_aout_binfmt);
 341module_exit(exit_aout_binfmt);
 342MODULE_LICENSE("GPL");
 343