binfmt_aout.c

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/*
 *  linux/fs/binfmt_aout.c
 *
 *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
 */

#include <linux/module.h>

#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/a.out.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/binfmts.h>
#include <linux/personality.h>
#include <linux/init.h>
#include <linux/coredump.h>
#include <linux/slab.h>

#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/a.out-core.h>

static int load_aout_binary(struct linux_binprm *, struct pt_regs * regs);
static int load_aout_library(struct file*);

#ifdef CONFIG_COREDUMP
/*
 * Routine writes a core dump image in the current directory.
 * Currently only a stub-function.
 *
 * Note that setuid/setgid files won't make a core-dump if the uid/gid
 * changed due to the set[u|g]id. It's enforced by the "current->mm->dumpable"
 * field, which also makes sure the core-dumps won't be recursive if the
 * dumping of the process results in another error..
 */
static int aout_core_dump(struct coredump_params *cprm)
{
    struct file *file = cprm->file;
    mm_segment_t fs;
    int has_dumped = 0;
    void __user *dump_start;
    int dump_size;
    struct user dump;
#ifdef __alpha__
#       define START_DATA(u)    ((void __user *)u.start_data)
#else
#   define START_DATA(u)    ((void __user *)((u.u_tsize << PAGE_SHIFT) + \
                 u.start_code))
#endif
#       define START_STACK(u)   ((void __user *)u.start_stack)

    fs = get_fs();
    set_fs(KERNEL_DS);
    has_dumped = 1;
    current->flags |= PF_DUMPCORE;
        strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
    dump.u_ar0 = offsetof(struct user, regs);
    dump.signal = cprm->siginfo->si_signo;
    aout_dump_thread(cprm->regs, &dump);

/* If the size of the dump file exceeds the rlimit, then see what would happen
   if we wrote the stack, but not the data area.  */
    if ((dump.u_dsize + dump.u_ssize+1) * PAGE_SIZE > cprm->limit)
        dump.u_dsize = 0;

/* Make sure we have enough room to write the stack and data areas. */
    if ((dump.u_ssize + 1) * PAGE_SIZE > cprm->limit)
        dump.u_ssize = 0;

/* make sure we actually have a data and stack area to dump */
    set_fs(USER_DS);
    if (!access_ok(VERIFY_READ, START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
        dump.u_dsize = 0;
    if (!access_ok(VERIFY_READ, START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
        dump.u_ssize = 0;

    set_fs(KERNEL_DS);
/* struct user */
    if (!dump_write(file, &dump, sizeof(dump)))
        goto end_coredump;
/* Now dump all of the user data.  Include malloced stuff as well */
    if (!dump_seek(cprm->file, PAGE_SIZE - sizeof(dump)))
        goto end_coredump;
/* now we start writing out the user space info */
    set_fs(USER_DS);
/* Dump the data area */
    if (dump.u_dsize != 0) {
        dump_start = START_DATA(dump);
        dump_size = dump.u_dsize << PAGE_SHIFT;
        if (!dump_write(file, dump_start, dump_size))
            goto end_coredump;
    }
/* Now prepare to dump the stack area */
    if (dump.u_ssize != 0) {
        dump_start = START_STACK(dump);
        dump_size = dump.u_ssize << PAGE_SHIFT;
        if (!dump_write(file, dump_start, dump_size))
            goto end_coredump;
    }
end_coredump:
    set_fs(fs);
    return has_dumped;
}
#else
#define aout_core_dump NULL
#endif

static struct linux_binfmt aout_format = {
    .module     = THIS_MODULE,
    .load_binary    = load_aout_binary,
    .load_shlib = load_aout_library,
    .core_dump  = aout_core_dump,
    .min_coredump   = PAGE_SIZE
};

#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)

static int set_brk(unsigned long start, unsigned long end)
{
    start = PAGE_ALIGN(start);
    end = PAGE_ALIGN(end);
    if (end > start) {
        unsigned long addr;
        addr = vm_brk(start, end - start);
        if (BAD_ADDR(addr))
            return addr;
    }
    return 0;
}

/*
 * create_aout_tables() parses the env- and arg-strings in new user
 * memory and creates the pointer tables from them, and puts their
 * addresses on the "stack", returning the new stack pointer value.
 */
static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
{
    char __user * __user *argv;
    char __user * __user *envp;
    unsigned long __user *sp;
    int argc = bprm->argc;
    int envc = bprm->envc;

    sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
#ifdef __alpha__
/* whee.. test-programs are so much fun. */
    put_user(0, --sp);
    put_user(0, --sp);
    if (bprm->loader) {
        put_user(0, --sp);
        put_user(1003, --sp);
        put_user(bprm->loader, --sp);
        put_user(1002, --sp);
    }
    put_user(bprm->exec, --sp);
    put_user(1001, --sp);
#endif
    sp -= envc+1;
    envp = (char __user * __user *) sp;
    sp -= argc+1;
    argv = (char __user * __user *) sp;
#ifndef __alpha__
    put_user((unsigned long) envp,--sp);
    put_user((unsigned long) argv,--sp);
#endif
    put_user(argc,--sp);
    current->mm->arg_start = (unsigned long) p;
    while (argc-->0) {
        char c;
        put_user(p,argv++);
        do {
            get_user(c,p++);
        } while (c);
    }
    put_user(NULL,argv);
    current->mm->arg_end = current->mm->env_start = (unsigned long) p;
    while (envc-->0) {
        char c;
        put_user(p,envp++);
        do {
            get_user(c,p++);
        } while (c);
    }
    put_user(NULL,envp);
    current->mm->env_end = (unsigned long) p;
    return sp;
}

/*
 * These are the functions used to load a.out style executables and shared
 * libraries.  There is no binary dependent code anywhere else.
 */

static int load_aout_binary(struct linux_binprm * bprm, struct pt_regs * regs)
{
    struct exec ex;
    unsigned long error;
    unsigned long fd_offset;
    unsigned long rlim;
    int retval;

    ex = *((struct exec *) bprm->buf);      /* exec-header */
    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
         N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
        N_TRSIZE(ex) || N_DRSIZE(ex) ||
        i_size_read(bprm->file->f_path.dentry->d_inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
        return -ENOEXEC;
    }

    /*
     * Requires a mmap handler. This prevents people from using a.out
     * as part of an exploit attack against /proc-related vulnerabilities.
     */
    if (!bprm->file->f_op || !bprm->file->f_op->mmap)
        return -ENOEXEC;

    fd_offset = N_TXTOFF(ex);

    /* Check initial limits. This avoids letting people circumvent
     * size limits imposed on them by creating programs with large
     * arrays in the data or bss.
     */
    rlim = rlimit(RLIMIT_DATA);
    if (rlim >= RLIM_INFINITY)
        rlim = ~0;
    if (ex.a_data + ex.a_bss > rlim)
        return -ENOMEM;

    /* Flush all traces of the currently running executable */
    retval = flush_old_exec(bprm);
    if (retval)
        return retval;

    /* OK, This is the point of no return */
#ifdef __alpha__
    SET_AOUT_PERSONALITY(bprm, ex);
#else
    set_personality(PER_LINUX);
#endif
    setup_new_exec(bprm);

    current->mm->end_code = ex.a_text +
        (current->mm->start_code = N_TXTADDR(ex));
    current->mm->end_data = ex.a_data +
        (current->mm->start_data = N_DATADDR(ex));
    current->mm->brk = ex.a_bss +
        (current->mm->start_brk = N_BSSADDR(ex));
    current->mm->free_area_cache = current->mm->mmap_base;
    current->mm->cached_hole_size = 0;

    retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
    if (retval < 0) {
        /* Someone check-me: is this error path enough? */
        send_sig(SIGKILL, current, 0);
        return retval;
    }

    install_exec_creds(bprm);

    if (N_MAGIC(ex) == OMAGIC) {
        unsigned long text_addr, map_size;
        loff_t pos;

        text_addr = N_TXTADDR(ex);

#ifdef __alpha__
        pos = fd_offset;
        map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
#else
        pos = 32;
        map_size = ex.a_text+ex.a_data;
#endif
        error = vm_brk(text_addr & PAGE_MASK, map_size);
        if (error != (text_addr & PAGE_MASK)) {
            send_sig(SIGKILL, current, 0);
            return error;
        }

        error = bprm->file->f_op->read(bprm->file,
              (char __user *)text_addr,
              ex.a_text+ex.a_data, &pos);
        if ((signed long)error < 0) {
            send_sig(SIGKILL, current, 0);
            return error;
        }
             
        flush_icache_range(text_addr, text_addr+ex.a_text+ex.a_data);
    } else {
        if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
            (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
        {
            printk(KERN_NOTICE "executable not page aligned\n");
        }

        if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
        {
            printk(KERN_WARNING 
                   "fd_offset is not page aligned. Please convert program: %s\n",
                   bprm->file->f_path.dentry->d_name.name);
        }

        if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
            loff_t pos = fd_offset;
            vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
            bprm->file->f_op->read(bprm->file,
                    (char __user *)N_TXTADDR(ex),
                    ex.a_text+ex.a_data, &pos);
            flush_icache_range((unsigned long) N_TXTADDR(ex),
                       (unsigned long) N_TXTADDR(ex) +
                       ex.a_text+ex.a_data);
            goto beyond_if;
        }

        error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
            PROT_READ | PROT_EXEC,
            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
            fd_offset);

        if (error != N_TXTADDR(ex)) {
            send_sig(SIGKILL, current, 0);
            return error;
        }

        error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
                PROT_READ | PROT_WRITE | PROT_EXEC,
                MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
                fd_offset + ex.a_text);
        if (error != N_DATADDR(ex)) {
            send_sig(SIGKILL, current, 0);
            return error;
        }
    }
beyond_if:
    set_binfmt(&aout_format);

    retval = set_brk(current->mm->start_brk, current->mm->brk);
    if (retval < 0) {
        send_sig(SIGKILL, current, 0);
        return retval;
    }

    current->mm->start_stack =
        (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
#ifdef __alpha__
    regs->gp = ex.a_gpvalue;
#endif
    start_thread(regs, ex.a_entry, current->mm->start_stack);
    return 0;
}

static int load_aout_library(struct file *file)
{
    struct inode * inode;
    unsigned long bss, start_addr, len;
    unsigned long error;
    int retval;
    struct exec ex;

    inode = file->f_path.dentry->d_inode;

    retval = -ENOEXEC;
    error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
    if (error != sizeof(ex))
        goto out;

    /* We come in here for the regular a.out style of shared libraries */
    if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
        N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
        i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
        goto out;
    }

    /*
     * Requires a mmap handler. This prevents people from using a.out
     * as part of an exploit attack against /proc-related vulnerabilities.
     */
    if (!file->f_op || !file->f_op->mmap)
        goto out;

    if (N_FLAGS(ex))
        goto out;

    /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
       this off to get the starting address for the page */

    start_addr =  ex.a_entry & 0xfffff000;

    if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
        loff_t pos = N_TXTOFF(ex);

        if (printk_ratelimit())
        {
            printk(KERN_WARNING 
                   "N_TXTOFF is not page aligned. Please convert library: %s\n",
                   file->f_path.dentry->d_name.name);
        }
        vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
        
        file->f_op->read(file, (char __user *)start_addr,
            ex.a_text + ex.a_data, &pos);
        flush_icache_range((unsigned long) start_addr,
                   (unsigned long) start_addr + ex.a_text + ex.a_data);

        retval = 0;
        goto out;
    }
    /* Now use mmap to map the library into memory. */
    error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
            PROT_READ | PROT_WRITE | PROT_EXEC,
            MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
            N_TXTOFF(ex));
    retval = error;
    if (error != start_addr)
        goto out;

    len = PAGE_ALIGN(ex.a_text + ex.a_data);
    bss = ex.a_text + ex.a_data + ex.a_bss;
    if (bss > len) {
        error = vm_brk(start_addr + len, bss - len);
        retval = error;
        if (error != start_addr + len)
            goto out;
    }
    retval = 0;
out:
    return retval;
}

static int __init init_aout_binfmt(void)
{
    register_binfmt(&aout_format);
    return 0;
}

static void __exit exit_aout_binfmt(void)
{
    unregister_binfmt(&aout_format);
}

core_initcall(init_aout_binfmt);
module_exit(exit_aout_binfmt);
MODULE_LICENSE("GPL");