/*
* linux/fs/exec.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* #!-checking implemented by tytso.
*/
/*
* Demand-loading implemented 01.12.91 - no need to read anything but
* the header into memory. The inode of the executable is put into
* "current->executable", and page faults do the actual loading. Clean.
*
* Once more I can proudly say that linux stood up to being changed: it
* was less than 2 hours work to get demand-loading completely implemented.
*
* Demand loading changed July 1993 by Eric Youngdale. Use mmap instead,
* current->executable is only used by the procfs. This allows a dispatch
* table to check for several different types of binary formats. We keep
* trying until we recognize the file or we run out of supported binary
* formats.
*/
#include <linux/config.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/a.out.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif
/*
* Here are the actual binaries that will be accepted:
* add more with "register_binfmt()" if using modules...
*
* These are defined again for the 'real' modules if you are using a
* module definition for these routines.
*/
static struct linux_binfmt *formats = (struct linux_binfmt *) NULL;
void __init binfmt_setup(void)
{
#ifdef CONFIG_BINFMT_MISC
init_misc_binfmt();
#endif
#ifdef CONFIG_BINFMT_ELF
init_elf_binfmt();
#endif
#ifdef CONFIG_BINFMT_ELF32
init_elf32_binfmt();
#endif
#ifdef CONFIG_BINFMT_AOUT
init_aout_binfmt();
#endif
#ifdef CONFIG_BINFMT_AOUT32
init_aout32_binfmt();
#endif
#ifdef CONFIG_BINFMT_EM86
init_em86_binfmt();
#endif
/* This cannot be configured out of the kernel */
init_script_binfmt();
}
int register_binfmt(struct linux_binfmt * fmt)
{
struct linux_binfmt ** tmp = &formats;
if (!fmt)
return -EINVAL;
if (fmt->next)
return -EBUSY;
while (*tmp) {
if (fmt == *tmp)
return -EBUSY;
tmp = &(*tmp)->next;
}
fmt->next = formats;
formats = fmt;
return 0;
}
#ifdef CONFIG_MODULES
int unregister_binfmt(struct linux_binfmt * fmt)
{
struct linux_binfmt ** tmp = &formats;
while (*tmp) {
if (fmt == *tmp) {
*tmp = fmt->next;
return 0;
}
tmp = &(*tmp)->next;
}
return -EINVAL;
}
#endif /* CONFIG_MODULES */
/* N.B. Error returns must be < 0 */
int open_dentry(struct dentry * dentry, int mode)
{
struct inode * inode = dentry->d_inode;
struct file * f;
int fd, error;
error = -EINVAL;
if (!inode->i_op || !inode->i_op->default_file_ops)
goto out;
fd = get_unused_fd();
if (fd >= 0) {
error = -ENFILE;
f = get_empty_filp();
if (!f)
goto out_fd;
f->f_flags = mode;
f->f_mode = (mode+1) & O_ACCMODE;
f->f_dentry = dentry;
f->f_pos = 0;
f->f_reada = 0;
f->f_op = inode->i_op->default_file_ops;
if (f->f_op->open) {
error = f->f_op->open(inode,f);
if (error)
goto out_filp;
}
fd_install(fd, f);
dget(dentry);
}
return fd;
out_filp:
if (error > 0)
error = -EIO;
put_filp(f);
out_fd:
put_unused_fd(fd);
out:
return error;
}
/*
* Note that a shared library must be both readable and executable due to
* security reasons.
*
* Also note that we take the address to load from from the file itself.
*/
asmlinkage int sys_uselib(const char * library)
{
int fd, retval;
struct file * file;
struct linux_binfmt * fmt;
lock_kernel();
fd = sys_open(library, 0, 0);
retval = fd;
if (fd < 0)
goto out;
file = fget(fd);
retval = -ENOEXEC;
if (file && file->f_dentry && file->f_op && file->f_op->read) {
for (fmt = formats ; fmt ; fmt = fmt->next) {
int (*fn)(int) = fmt->load_shlib;
if (!fn)
continue;
/* N.B. Should use file instead of fd */
retval = fn(fd);
if (retval != -ENOEXEC)
break;
}
}
fput(file);
sys_close(fd);
out:
unlock_kernel();
return retval;
}
/*
* count() counts the number of arguments/envelopes
*/
static int count(char ** argv)
{
int i = 0;
if (argv != NULL) {
for (;;) {
char * p;
int error;
error = get_user(p,argv);
if (error)
return error;
if (!p)
break;
argv++;
i++;
}
}
return i;
}
/*
* 'copy_strings()' copies argument/envelope strings from user
* memory to free pages in kernel mem. These are in a format ready
* to be put directly into the top of new user memory.
*/
int copy_strings(int argc,char ** argv, struct linux_binprm *bprm)
{
while (argc-- > 0) {
char *str;
int len;
unsigned long pos;
if (get_user(str, argv+argc) || !str || !(len = strlen_user(str)))
return -EFAULT;
if (bprm->p < len)
return -E2BIG;
bprm->p -= len;
/* XXX: add architecture specific overflow check here. */
pos = bprm->p;
while (len) {
char *pag;
int offset, bytes_to_copy;
offset = pos % PAGE_SIZE;
if (!(pag = (char *) bprm->page[pos/PAGE_SIZE]) &&
!(pag = (char *) bprm->page[pos/PAGE_SIZE] =
(unsigned long *) get_free_page(GFP_USER)))
return -ENOMEM;
bytes_to_copy = PAGE_SIZE - offset;
if (bytes_to_copy > len)
bytes_to_copy = len;
if (copy_from_user(pag + offset, str, bytes_to_copy))
return -EFAULT;
pos += bytes_to_copy;
str += bytes_to_copy;
len -= bytes_to_copy;
}
}
return 0;
}
/*
* Like copy_strings, but get argv and its values from kernel memory.
*/
int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
{
int r;
mm_segment_t oldfs = get_fs();
set_fs(KERNEL_DS);
r = copy_strings(argc, argv, bprm);
set_fs(oldfs);
return r;
}
int setup_arg_pages(struct linux_binprm *bprm)
{
unsigned long stack_base;
struct vm_area_struct *mpnt;
int i;
stack_base = STACK_TOP - MAX_ARG_PAGES*PAGE_SIZE;
bprm->p += stack_base;
if (bprm->loader)
bprm->loader += stack_base;
bprm->exec += stack_base;
mpnt = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (!mpnt)
return -ENOMEM;
{
mpnt->vm_mm = current->mm;
mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
mpnt->vm_end = STACK_TOP;
mpnt->vm_page_prot = PAGE_COPY;
mpnt->vm_flags = VM_STACK_FLAGS;
mpnt->vm_ops = NULL;
mpnt->vm_offset = 0;
mpnt->vm_file = NULL;
mpnt->vm_pte = 0;
insert_vm_struct(current->mm, mpnt);
current->mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
}
for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
if (bprm->page[i]) {
current->mm->rss++;
put_dirty_page(current,bprm->page[i],stack_base);
}
stack_base += PAGE_SIZE;
}
return 0;
}
/*
* Read in the complete executable. This is used for "-N" files
* that aren't on a block boundary, and for files on filesystems
* without get_block support.
*/
int read_exec(struct dentry *dentry, unsigned long offset,
char * addr, unsigned long count, int to_kmem)
{
struct file file;
struct inode * inode = dentry->d_inode;
int result = -ENOEXEC;
if (!inode->i_op || !inode->i_op->default_file_ops)
goto end_readexec;
if (init_private_file(&file, dentry, 1))
goto end_readexec;
if (!file.f_op->read)
goto close_readexec;
if (file.f_op->llseek) {
if (file.f_op->llseek(&file,offset,0) != offset)
goto close_readexec;
} else
file.f_pos = offset;
if (to_kmem) {
mm_segment_t old_fs = get_fs();
set_fs(get_ds());
result = file.f_op->read(&file, addr, count, &file.f_pos);
set_fs(old_fs);
} else {
result = verify_area(VERIFY_WRITE, addr, count);
if (result)
goto close_readexec;
result = file.f_op->read(&file, addr, count, &file.f_pos);
}
close_readexec:
if (file.f_op->release)
file.f_op->release(inode,&file);
end_readexec:
return result;
}
static int exec_mmap(void)
{
struct mm_struct * mm, * old_mm;
int retval, nr;
if (atomic_read(¤t->mm->count) == 1) {
flush_cache_mm(current->mm);
mm_release();
release_segments(current->mm);
exit_mmap(current->mm);
flush_tlb_mm(current->mm);
return 0;
}
retval = -ENOMEM;
mm = mm_alloc();
if (!mm)
goto fail_nomem;
mm->cpu_vm_mask = (1UL << smp_processor_id());
mm->total_vm = 0;
mm->rss = 0;
/*
* Make sure we have a private ldt if needed ...
*/
nr = current->tarray_ptr - &task[0];
copy_segments(nr, current, mm);
old_mm = current->mm;
current->mm = mm;
retval = new_page_tables(current);
if (retval)
goto fail_restore;
activate_context(current);
up(&mm->mmap_sem);
mm_release();
mmput(old_mm);
return 0;
/*
* Failure ... restore the prior mm_struct.
*/
fail_restore:
current->mm = old_mm;
/* restore the ldt for this task */
copy_segments(nr, current, NULL);
release_segments(mm);
kmem_cache_free(mm_cachep, mm);
fail_nomem:
return retval;
}
/*
* This function makes sure the current process has its own signal table,
* so that flush_signal_handlers can later reset the handlers without
* disturbing other processes. (Other processes might share the signal
* table via the CLONE_SIGHAND option to clone().)
*/
static inline int make_private_signals(void)
{
struct signal_struct * newsig;
if (atomic_read(¤t->sig->count) <= 1)
return 0;
newsig = kmalloc(sizeof(*newsig), GFP_KERNEL);
if (newsig == NULL)
return -ENOMEM;
spin_lock_init(&newsig->siglock);
atomic_set(&newsig->count, 1);
memcpy(newsig->action, current->sig->action, sizeof(newsig->action));
current->sig = newsig;
return 0;
}
/*
* If make_private_signals() made a copy of the signal table, decrement the
* refcount of the original table, and free it if necessary.
* We don't do that in make_private_signals() so that we can back off
* in flush_old_exec() if an error occurs after calling make_private_signals().
*/
static inline void release_old_signals(struct signal_struct * oldsig)
{
if (current->sig == oldsig)
return;
if (atomic_dec_and_test(&oldsig->count))
kfree(oldsig);
}
/*
* These functions flushes out all traces of the currently running executable
* so that a new one can be started
*/
static inline void flush_old_files(struct files_struct * files)
{
unsigned long j;
j = 0;
for (;;) {
unsigned long set, i;
i = j * __NFDBITS;
if (i >= files->max_fds)
break;
set = files->close_on_exec.fds_bits[j];
files->close_on_exec.fds_bits[j] = 0;
j++;
for ( ; set ; i++,set >>= 1) {
if (set & 1)
sys_close(i);
}
}
}
int flush_old_exec(struct linux_binprm * bprm)
{
char * name;
int i, ch, retval;
struct signal_struct * oldsig;
/*
* Make sure we have a private signal table
*/
oldsig = current->sig;
retval = make_private_signals();
if (retval) goto flush_failed;
/*
* Release all of the old mmap stuff
*/
retval = exec_mmap();
if (retval) goto mmap_failed;
/* This is the point of no return */
release_old_signals(oldsig);
if (current->euid == current->uid && current->egid == current->gid)
current->dumpable = 1;
name = bprm->filename;
for (i=0; (ch = *(name++)) != '\0';) {
if (ch == '/')
i = 0;
else
if (i < 15)
current->comm[i++] = ch;
}
current->comm[i] = '\0';
flush_thread();
if (bprm->e_uid != current->euid || bprm->e_gid != current->egid ||
permission(bprm->dentry->d_inode,MAY_READ))
current->dumpable = 0;
flush_signal_handlers(current);
flush_old_files(current->files);
return 0;
mmap_failed:
if (current->sig != oldsig)
kfree(current->sig);
flush_failed:
current->sig = oldsig;
return retval;
}
/*
* We mustn't allow tracing of suid binaries, unless
* the tracer has the capability to trace anything..
*/
static inline int must_not_trace_exec(struct task_struct * p)
{
return (p->flags & PF_PTRACED) && !cap_raised(p->p_pptr->cap_effective, CAP_SYS_PTRACE);
}
/*
* Fill the binprm structure from the inode.
* Check permissions, then read the first 512 bytes
*/
int prepare_binprm(struct linux_binprm *bprm)
{
int mode;
int retval,id_change,cap_raised;
struct inode * inode = bprm->dentry->d_inode;
mode = inode->i_mode;
if (!S_ISREG(mode)) /* must be regular file */
return -EACCES;
if (!(mode & 0111)) /* with at least _one_ execute bit set */
return -EACCES;
if (IS_NOEXEC(inode)) /* FS mustn't be mounted noexec */
return -EACCES;
if (!inode->i_sb)
return -EACCES;
if ((retval = permission(inode, MAY_EXEC)) != 0)
return retval;
/* better not execute files which are being written to */
if (inode->i_writecount > 0)
return -ETXTBSY;
bprm->e_uid = current->euid;
bprm->e_gid = current->egid;
id_change = cap_raised = 0;
/* Set-uid? */
if (mode & S_ISUID) {
bprm->e_uid = inode->i_uid;
if (bprm->e_uid != current->euid)
id_change = 1;
}
/* Set-gid? */
/*
* If setgid is set but no group execute bit then this
* is a candidate for mandatory locking, not a setgid
* executable.
*/
if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
bprm->e_gid = inode->i_gid;
if (!in_group_p(bprm->e_gid))
id_change = 1;
}
/* We don't have VFS support for capabilities yet */
cap_clear(bprm->cap_inheritable);
cap_clear(bprm->cap_permitted);
cap_clear(bprm->cap_effective);
/* To support inheritance of root-permissions and suid-root
* executables under compatibility mode, we raise the
* effective and inherited bitmasks of the executable file
* (translation: we set the executable "capability dumb" and
* set the allowed set to maximum). We don't set any forced
* bits.
*
* If only the real uid is 0, we only raise the inheritable
* bitmask of the executable file (translation: we set the
* allowed set to maximum and the application to "capability
* smart").
*/
if (!issecure(SECURE_NOROOT)) {
if (bprm->e_uid == 0 || current->uid == 0)
cap_set_full(bprm->cap_inheritable);
if (bprm->e_uid == 0)
cap_set_full(bprm->cap_effective);
}
/* Only if pP' is _not_ a subset of pP, do we consider there
* has been a capability related "change of capability". In
* such cases, we need to check that the elevation of
* privilege does not go against other system constraints.
* The new Permitted set is defined below -- see (***). */
{
kernel_cap_t working =
cap_combine(bprm->cap_permitted,
cap_intersect(bprm->cap_inheritable,
current->cap_inheritable));
if (!cap_issubset(working, current->cap_permitted)) {
cap_raised = 1;
}
}
if (id_change || cap_raised) {
/* We can't suid-execute if we're sharing parts of the executable */
/* or if we're being traced (or if suid execs are not allowed) */
/* (current->mm->count > 1 is ok, as we'll get a new mm anyway) */
if (IS_NOSUID(inode)
|| must_not_trace_exec(current)
|| (atomic_read(¤t->fs->count) > 1)
|| (atomic_read(¤t->sig->count) > 1)
|| (atomic_read(¤t->files->count) > 1)) {
if (id_change && !capable(CAP_SETUID))
return -EPERM;
if (cap_raised && !capable(CAP_SETPCAP))
return -EPERM;
}
}
memset(bprm->buf,0,sizeof(bprm->buf));
return read_exec(bprm->dentry,0,bprm->buf,128,1);
}
/*
* This function is used to produce the new IDs and capabilities
* from the old ones and the file's capabilities.
*
* The formula used for evolving capabilities is:
*
* pI' = pI
* (***) pP' = fP | (fI & pI)
* pE' = pP' & fE [NB. fE is 0 or ~0]
*
* I=Inheritable, P=Permitted, E=Effective // p=process, f=file
* ' indicates post-exec().
*/
void compute_creds(struct linux_binprm *bprm)
{
int new_permitted = cap_t(bprm->cap_permitted) |
(cap_t(bprm->cap_inheritable) &
cap_t(current->cap_inheritable));
/* For init, we want to retain the capabilities set
* in the init_task struct. Thus we skip the usual
* capability rules */
if (current->pid != 1) {
cap_t(current->cap_permitted) = new_permitted;
cap_t(current->cap_effective) = new_permitted &
cap_t(bprm->cap_effective);
}
/* AUD: Audit candidate if current->cap_effective is set */
current->suid = current->euid = current->fsuid = bprm->e_uid;
current->sgid = current->egid = current->fsgid = bprm->e_gid;
if (current->euid != current->uid || current->egid != current->gid ||
!cap_issubset(new_permitted, current->cap_permitted))
current->dumpable = 0;
}
void remove_arg_zero(struct linux_binprm *bprm)
{
if (bprm->argc) {
unsigned long offset;
char * page;
offset = bprm->p % PAGE_SIZE;
page = (char*)bprm->page[bprm->p/PAGE_SIZE];
while(bprm->p++,*(page+offset++))
if(offset==PAGE_SIZE){
offset=0;
page = (char*)bprm->page[bprm->p/PAGE_SIZE];
}
bprm->argc--;
}
}
/*
* cycle the list of binary formats handler, until one recognizes the image
*/
int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
{
int try,retval=0;
struct linux_binfmt *fmt;
#ifdef __alpha__
/* handle /sbin/loader.. */
{
struct exec * eh = (struct exec *) bprm->buf;
struct linux_binprm bprm_loader;
if (!bprm->loader && eh->fh.f_magic == 0x183 &&
(eh->fh.f_flags & 0x3000) == 0x3000)
{
int i;
char * dynloader[] = { "/sbin/loader" };
struct dentry * dentry;
dput(bprm->dentry);
bprm->dentry = NULL;
bprm_loader.p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
for (i=0 ; i<MAX_ARG_PAGES ; i++) /* clear page-table */
bprm_loader.page[i] = 0;
dentry = open_namei(dynloader[0], 0, 0);
retval = PTR_ERR(dentry);
if (IS_ERR(dentry))
return retval;
bprm->dentry = dentry;
bprm->loader = bprm_loader.p;
retval = prepare_binprm(bprm);
if (retval<0)
return retval;
/* should call search_binary_handler recursively here,
but it does not matter */
}
}
#endif
for (try=0; try<2; try++) {
for (fmt = formats ; fmt ; fmt = fmt->next) {
int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
if (!fn)
continue;
retval = fn(bprm, regs);
if (retval >= 0) {
if (bprm->dentry)
dput(bprm->dentry);
bprm->dentry = NULL;
current->did_exec = 1;
return retval;
}
if (retval != -ENOEXEC)
break;
if (!bprm->dentry) /* We don't have the dentry anymore */
return retval;
}
if (retval != -ENOEXEC) {
break;
#ifdef CONFIG_KMOD
}else{
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
char modname[20];
if (printable(bprm->buf[0]) &&
printable(bprm->buf[1]) &&
printable(bprm->buf[2]) &&
printable(bprm->buf[3]))
break; /* -ENOEXEC */
sprintf(modname, "binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
request_module(modname);
#endif
}
}
return retval;
}
/*
* sys_execve() executes a new program.
*/
int do_execve(char * filename, char ** argv, char ** envp, struct pt_regs * regs)
{
struct linux_binprm bprm;
struct dentry * dentry;
int retval;
int i;
bprm.p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
memset(bprm.page, 0, MAX_ARG_PAGES*sizeof(bprm.page[0]));
dentry = open_namei(filename, 0, 0);
retval = PTR_ERR(dentry);
if (IS_ERR(dentry))
return retval;
bprm.dentry = dentry;
bprm.filename = filename;
bprm.sh_bang = 0;
bprm.loader = 0;
bprm.exec = 0;
if ((bprm.argc = count(argv)) < 0) {
dput(dentry);
return bprm.argc;
}
if ((bprm.envc = count(envp)) < 0) {
dput(dentry);
return bprm.envc;
}
retval = prepare_binprm(&bprm);
if (retval < 0)
goto out;
retval = copy_strings_kernel(1, &bprm.filename, &bprm);
if (retval < 0)
goto out;
bprm.exec = bprm.p;
retval = copy_strings(bprm.envc, envp, &bprm);
if (retval < 0)
goto out;
retval = copy_strings(bprm.argc, argv, &bprm);
if (retval < 0)
goto out;
retval = search_binary_handler(&bprm,regs);
if (retval >= 0)
/* execve success */
return retval;
out:
/* Something went wrong, return the inode and free the argument pages*/
if (bprm.dentry)
dput(bprm.dentry);
/* Assumes that free_page() can take a NULL argument. */
/* I hope this is ok for all architectures */
for (i=0 ; i<MAX_ARG_PAGES ; i++)
free_page(bprm.page[i]);
return retval;
}