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linux/fs/exec.c

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/*
* 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/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 <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/swap.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/proc_fs.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/rmap.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/signalfd.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif
int core_uses_pid;
char core_pattern[CORENAME_MAX_SIZE] = "core";
int suid_dumpable = 0;
EXPORT_SYMBOL(suid_dumpable);
/* The maximal length of core_pattern is also specified in sysctl.c */
static struct linux_binfmt *formats;
static DEFINE_RWLOCK(binfmt_lock);
int register_binfmt(struct linux_binfmt * fmt)
{
struct linux_binfmt ** tmp = &formats;
if (!fmt)
return -EINVAL;
if (fmt->next)
return -EBUSY;
write_lock(&binfmt_lock);
while (*tmp) {
if (fmt == *tmp) {
write_unlock(&binfmt_lock);
return -EBUSY;
}
tmp = &(*tmp)->next;
}
fmt->next = formats;
formats = fmt;
write_unlock(&binfmt_lock);
return 0;
}
EXPORT_SYMBOL(register_binfmt);
int unregister_binfmt(struct linux_binfmt * fmt)
{
struct linux_binfmt ** tmp = &formats;
write_lock(&binfmt_lock);
while (*tmp) {
if (fmt == *tmp) {
*tmp = fmt->next;
fmt->next = NULL;
write_unlock(&binfmt_lock);
return 0;
}
tmp = &(*tmp)->next;
}
write_unlock(&binfmt_lock);
return -EINVAL;
}
EXPORT_SYMBOL(unregister_binfmt);
static inline void put_binfmt(struct linux_binfmt * fmt)
{
module_put(fmt->module);
}
/*
* 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 long sys_uselib(const char __user * library)
{
struct file * file;
struct nameidata nd;
int error;
error = __user_path_lookup_open(library, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
if (error)
goto out;
error = -EACCES;
if (nd.mnt->mnt_flags & MNT_NOEXEC)
goto exit;
error = -EINVAL;
if (!S_ISREG(nd.dentry->d_inode->i_mode))
goto exit;
error = vfs_permission(&nd, MAY_READ | MAY_EXEC);
if (error)
goto exit;
file = nameidata_to_filp(&nd, O_RDONLY);
error = PTR_ERR(file);
if (IS_ERR(file))
goto out;
error = -ENOEXEC;
if(file->f_op) {
struct linux_binfmt * fmt;
read_lock(&binfmt_lock);
for (fmt = formats ; fmt ; fmt = fmt->next) {
if (!fmt->load_shlib)
continue;
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
error = fmt->load_shlib(file);
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (error != -ENOEXEC)
break;
}
read_unlock(&binfmt_lock);
}
fput(file);
out:
return error;
exit:
release_open_intent(&nd);
path_release(&nd);
goto out;
}
#ifdef CONFIG_MMU
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
int ret;
#ifdef CONFIG_STACK_GROWSUP
if (write) {
ret = expand_stack_downwards(bprm->vma, pos);
if (ret < 0)
return NULL;
}
#endif
ret = get_user_pages(current, bprm->mm, pos,
1, write, 1, &page, NULL);
if (ret <= 0)
return NULL;
if (write) {
struct rlimit *rlim = current->signal->rlim;
unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
/*
* Limit to 1/4-th the stack size for the argv+env strings.
* This ensures that:
* - the remaining binfmt code will not run out of stack space,
* - the program will have a reasonable amount of stack left
* to work from.
*/
if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
put_page(page);
return NULL;
}
}
return page;
}
static void put_arg_page(struct page *page)
{
put_page(page);
}
static void free_arg_page(struct linux_binprm *bprm, int i)
{
}
static void free_arg_pages(struct linux_binprm *bprm)
{
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
flush_cache_page(bprm->vma, pos, page_to_pfn(page));
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
int err = -ENOMEM;
struct vm_area_struct *vma = NULL;
struct mm_struct *mm = bprm->mm;
bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (!vma)
goto err;
down_write(&mm->mmap_sem);
vma->vm_mm = mm;
/*
* Place the stack at the largest stack address the architecture
* supports. Later, we'll move this to an appropriate place. We don't
* use STACK_TOP because that can depend on attributes which aren't
* configured yet.
*/
vma->vm_end = STACK_TOP_MAX;
vma->vm_start = vma->vm_end - PAGE_SIZE;
vma->vm_flags = VM_STACK_FLAGS;
vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
err = insert_vm_struct(mm, vma);
if (err) {
up_write(&mm->mmap_sem);
goto err;
}
mm->stack_vm = mm->total_vm = 1;
up_write(&mm->mmap_sem);
bprm->p = vma->vm_end - sizeof(void *);
return 0;
err:
if (vma) {
bprm->vma = NULL;
kmem_cache_free(vm_area_cachep, vma);
}
return err;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= MAX_ARG_STRLEN;
}
#else
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
page = bprm->page[pos / PAGE_SIZE];
if (!page && write) {
page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
if (!page)
return NULL;
bprm->page[pos / PAGE_SIZE] = page;
}
return page;
}
static void put_arg_page(struct page *page)
{
}
static void free_arg_page(struct linux_binprm *bprm, int i)
{
if (bprm->page[i]) {
__free_page(bprm->page[i]);
bprm->page[i] = NULL;
}
}
static void free_arg_pages(struct linux_binprm *bprm)
{
int i;
for (i = 0; i < MAX_ARG_PAGES; i++)
free_arg_page(bprm, i);
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
return 0;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= bprm->p;
}
#endif /* CONFIG_MMU */
/*
* Create a new mm_struct and populate it with a temporary stack
* vm_area_struct. We don't have enough context at this point to set the stack
* flags, permissions, and offset, so we use temporary values. We'll update
* them later in setup_arg_pages().
*/
int bprm_mm_init(struct linux_binprm *bprm)
{
int err;
struct mm_struct *mm = NULL;
bprm->mm = mm = mm_alloc();
err = -ENOMEM;
if (!mm)
goto err;
err = init_new_context(current, mm);
if (err)
goto err;
err = __bprm_mm_init(bprm);
if (err)
goto err;
return 0;
err:
if (mm) {
bprm->mm = NULL;
mmdrop(mm);
}
return err;
}
/*
* count() counts the number of strings in array ARGV.
*/
static int count(char __user * __user * argv, int max)
{
int i = 0;
if (argv != NULL) {
for (;;) {
char __user * p;
if (get_user(p, argv))
return -EFAULT;
if (!p)
break;
argv++;
if(++i > max)
return -E2BIG;
cond_resched();
}
}
return i;
}
/*
* 'copy_strings()' copies argument/environment strings from the old
* processes's memory to the new process's stack. The call to get_user_pages()
* ensures the destination page is created and not swapped out.
*/
static int copy_strings(int argc, char __user * __user * argv,
struct linux_binprm *bprm)
{
struct page *kmapped_page = NULL;
char *kaddr = NULL;
unsigned long kpos = 0;
int ret;
while (argc-- > 0) {
char __user *str;
int len;
unsigned long pos;
if (get_user(str, argv+argc) ||
!(len = strnlen_user(str, MAX_ARG_STRLEN))) {
ret = -EFAULT;
goto out;
}
if (!valid_arg_len(bprm, len)) {
ret = -E2BIG;
goto out;
}
/* We're going to work our way backwords. */
pos = bprm->p;
str += len;
bprm->p -= len;
while (len > 0) {
int offset, bytes_to_copy;
offset = pos % PAGE_SIZE;
if (offset == 0)
offset = PAGE_SIZE;
bytes_to_copy = offset;
if (bytes_to_copy > len)
bytes_to_copy = len;
offset -= bytes_to_copy;
pos -= bytes_to_copy;
str -= bytes_to_copy;
len -= bytes_to_copy;
if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
struct page *page;
page = get_arg_page(bprm, pos, 1);
if (!page) {
ret = -E2BIG;
goto out;
}
if (kmapped_page) {
flush_kernel_dcache_page(kmapped_page);
kunmap(kmapped_page);
put_arg_page(kmapped_page);
}
kmapped_page = page;
kaddr = kmap(kmapped_page);
kpos = pos & PAGE_MASK;
flush_arg_page(bprm, kpos, kmapped_page);
}
if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
ret = -EFAULT;
goto out;
}
}
}
ret = 0;
out:
if (kmapped_page) {
flush_kernel_dcache_page(kmapped_page);
kunmap(kmapped_page);
put_arg_page(kmapped_page);
}
return ret;
}
/*
* 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, (char __user * __user *)argv, bprm);
set_fs(oldfs);
return r;
}
EXPORT_SYMBOL(copy_strings_kernel);
#ifdef CONFIG_MMU
/*
* During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
* the binfmt code determines where the new stack should reside, we shift it to
* its final location. The process proceeds as follows:
*
* 1) Use shift to calculate the new vma endpoints.
* 2) Extend vma to cover both the old and new ranges. This ensures the
* arguments passed to subsequent functions are consistent.
* 3) Move vma's page tables to the new range.
* 4) Free up any cleared pgd range.
* 5) Shrink the vma to cover only the new range.
*/
static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long old_start = vma->vm_start;
unsigned long old_end = vma->vm_end;
unsigned long length = old_end - old_start;
unsigned long new_start = old_start - shift;
unsigned long new_end = old_end - shift;
struct mmu_gather *tlb;
BUG_ON(new_start > new_end);
/*
* ensure there are no vmas between where we want to go
* and where we are
*/
if (vma != find_vma(mm, new_start))
return -EFAULT;
/*
* cover the whole range: [new_start, old_end)
*/
vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
/*
* move the page tables downwards, on failure we rely on
* process cleanup to remove whatever mess we made.
*/
if (length != move_page_tables(vma, old_start,
vma, new_start, length))
return -ENOMEM;
lru_add_drain();
tlb = tlb_gather_mmu(mm, 0);
if (new_end > old_start) {
/*
* when the old and new regions overlap clear from new_end.
*/
free_pgd_range(&tlb, new_end, old_end, new_end,
vma->vm_next ? vma->vm_next->vm_start : 0);
} else {
/*
* otherwise, clean from old_start; this is done to not touch
* the address space in [new_end, old_start) some architectures
* have constraints on va-space that make this illegal (IA64) -
* for the others its just a little faster.
*/
free_pgd_range(&tlb, old_start, old_end, new_end,
vma->vm_next ? vma->vm_next->vm_start : 0);
}
tlb_finish_mmu(tlb, new_end, old_end);
/*
* shrink the vma to just the new range.
*/
vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
return 0;
}
#define EXTRA_STACK_VM_PAGES 20 /* random */
/*
* Finalizes the stack vm_area_struct. The flags and permissions are updated,
* the stack is optionally relocated, and some extra space is added.
*/
int setup_arg_pages(struct linux_binprm *bprm,
unsigned long stack_top,
int executable_stack)
{
unsigned long ret;
unsigned long stack_shift;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = bprm->vma;
struct vm_area_struct *prev = NULL;
unsigned long vm_flags;
unsigned long stack_base;
#ifdef CONFIG_STACK_GROWSUP
/* Limit stack size to 1GB */
stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
if (stack_base > (1 << 30))
stack_base = 1 << 30;
/* Make sure we didn't let the argument array grow too large. */
if (vma->vm_end - vma->vm_start > stack_base)
return -ENOMEM;
stack_base = PAGE_ALIGN(stack_top - stack_base);
stack_shift = vma->vm_start - stack_base;
mm->arg_start = bprm->p - stack_shift;
bprm->p = vma->vm_end - stack_shift;
#else
stack_top = arch_align_stack(stack_top);
stack_top = PAGE_ALIGN(stack_top);
stack_shift = vma->vm_end - stack_top;
bprm->p -= stack_shift;
mm->arg_start = bprm->p;
#endif
if (bprm->loader)
bprm->loader -= stack_shift;
bprm->exec -= stack_shift;
down_write(&mm->mmap_sem);
vm_flags = vma->vm_flags;
/*
* Adjust stack execute permissions; explicitly enable for
* EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
* (arch default) otherwise.
*/
if (unlikely(executable_stack == EXSTACK_ENABLE_X))
vm_flags |= VM_EXEC;
else if (executable_stack == EXSTACK_DISABLE_X)
vm_flags &= ~VM_EXEC;
vm_flags |= mm->def_flags;
ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
vm_flags);
if (ret)
goto out_unlock;
BUG_ON(prev != vma);
/* Move stack pages down in memory. */
if (stack_shift) {
ret = shift_arg_pages(vma, stack_shift);
if (ret) {
up_write(&mm->mmap_sem);
return ret;
}
}
#ifdef CONFIG_STACK_GROWSUP
stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#else
stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#endif
ret = expand_stack(vma, stack_base);
if (ret)
ret = -EFAULT;
out_unlock:
up_write(&mm->mmap_sem);
return 0;
}
EXPORT_SYMBOL(setup_arg_pages);
#endif /* CONFIG_MMU */
struct file *open_exec(const char *name)
{
struct nameidata nd;
int err;
struct file *file;
err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
file = ERR_PTR(err);
if (!err) {
struct inode *inode = nd.dentry->d_inode;
file = ERR_PTR(-EACCES);
if (!(nd.mnt->mnt_flags & MNT_NOEXEC) &&
S_ISREG(inode->i_mode)) {
int err = vfs_permission(&nd, MAY_EXEC);
file = ERR_PTR(err);
if (!err) {
file = nameidata_to_filp(&nd, O_RDONLY);
if (!IS_ERR(file)) {
err = deny_write_access(file);
if (err) {
fput(file);
file = ERR_PTR(err);
}
}
out:
return file;
}
}
release_open_intent(&nd);
path_release(&nd);
}
goto out;
}
EXPORT_SYMBOL(open_exec);
int kernel_read(struct file *file, unsigned long offset,
char *addr, unsigned long count)
{
mm_segment_t old_fs;
loff_t pos = offset;
int result;
old_fs = get_fs();
set_fs(get_ds());
/* The cast to a user pointer is valid due to the set_fs() */
result = vfs_read(file, (void __user *)addr, count, &pos);
set_fs(old_fs);
return result;
}
EXPORT_SYMBOL(kernel_read);
static int exec_mmap(struct mm_struct *mm)
{
struct task_struct *tsk;
struct mm_struct * old_mm, *active_mm;
/* Notify parent that we're no longer interested in the old VM */
tsk = current;
old_mm = current->mm;
mm_release(tsk, old_mm);
if (old_mm) {
/*
* Make sure that if there is a core dump in progress
* for the old mm, we get out and die instead of going
* through with the exec. We must hold mmap_sem around
* checking core_waiters and changing tsk->mm. The
* core-inducing thread will increment core_waiters for
* each thread whose ->mm == old_mm.
*/
down_read(&old_mm->mmap_sem);
if (unlikely(old_mm->core_waiters)) {
up_read(&old_mm->mmap_sem);
return -EINTR;
}
}
task_lock(tsk);
active_mm = tsk->active_mm;
tsk->mm = mm;
tsk->active_mm = mm;
activate_mm(active_mm, mm);
task_unlock(tsk);
arch_pick_mmap_layout(mm);
if (old_mm) {
up_read(&old_mm->mmap_sem);
BUG_ON(active_mm != old_mm);
mmput(old_mm);
return 0;
}
mmdrop(active_mm);
return 0;
}
/*
* 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 int de_thread(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct sighand_struct *newsighand, *oldsighand = tsk->sighand;
spinlock_t *lock = &oldsighand->siglock;
struct task_struct *leader = NULL;
int count;
/*
* Tell all the sighand listeners that this sighand has
* been detached. The signalfd_detach() function grabs the
* sighand lock, if signal listeners are present on the sighand.
*/
signalfd_detach(tsk);
/*
* If we don't share sighandlers, then we aren't sharing anything
* and we can just re-use it all.
*/
if (atomic_read(&oldsighand->count) <= 1) {
BUG_ON(atomic_read(&sig->count) != 1);
exit_itimers(sig);
return 0;
}
newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
if (!newsighand)
return -ENOMEM;
if (thread_group_empty(tsk))
goto no_thread_group;
/*
* Kill all other threads in the thread group.
* We must hold tasklist_lock to call zap_other_threads.
*/
read_lock(&tasklist_lock);
spin_lock_irq(lock);
if (sig->flags & SIGNAL_GROUP_EXIT) {
/*
* Another group action in progress, just
* return so that the signal is processed.
*/
spin_unlock_irq(lock);
read_unlock(&tasklist_lock);
kmem_cache_free(sighand_cachep, newsighand);
return -EAGAIN;
}
/*
* child_reaper ignores SIGKILL, change it now.
* Reparenting needs write_lock on tasklist_lock,
* so it is safe to do it under read_lock.
*/
if (unlikely(tsk->group_leader == child_reaper(tsk)))
tsk->nsproxy->pid_ns->child_reaper = tsk;
zap_other_threads(tsk);
read_unlock(&tasklist_lock);
/*
* Account for the thread group leader hanging around:
*/
count = 1;
if (!thread_group_leader(tsk)) {
count = 2;
/*
* The SIGALRM timer survives the exec, but needs to point
* at us as the new group leader now. We have a race with
* a timer firing now getting the old leader, so we need to
* synchronize with any firing (by calling del_timer_sync)
* before we can safely let the old group leader die.
*/
sig->tsk = tsk;
spin_unlock_irq(lock);
if (hrtimer_cancel(&sig->real_timer))
hrtimer_restart(&sig->real_timer);
spin_lock_irq(lock);
}
while (atomic_read(&sig->count) > count) {
sig->group_exit_task = tsk;
sig->notify_count = count;
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(lock);
schedule();
spin_lock_irq(lock);
}
sig->group_exit_task = NULL;
sig->notify_count = 0;
spin_unlock_irq(lock);
/*
* At this point all other threads have exited, all we have to
* do is to wait for the thread group leader to become inactive,
* and to assume its PID:
*/
if (!thread_group_leader(tsk)) {
/*
* Wait for the thread group leader to be a zombie.
* It should already be zombie at this point, most
* of the time.
*/
leader = tsk->group_leader;
while (leader->exit_state != EXIT_ZOMBIE)
yield();
/*
* The only record we have of the real-time age of a
* process, regardless of execs it's done, is start_time.
* All the past CPU time is accumulated in signal_struct
* from sister threads now dead. But in this non-leader
* exec, nothing survives from the original leader thread,
* whose birth marks the true age of this process now.
* When we take on its identity by switching to its PID, we
* also take its birthdate (always earlier than our own).
*/
tsk->start_time = leader->start_time;
write_lock_irq(&tasklist_lock);
BUG_ON(leader->tgid != tsk->tgid);
BUG_ON(tsk->pid == tsk->tgid);
/*
* An exec() starts a new thread group with the
* TGID of the previous thread group. Rehash the
* two threads with a switched PID, and release
* the former thread group leader:
*/
/* Become a process group leader with the old leader's pid.
* The old leader becomes a thread of the this thread group.
* Note: The old leader also uses this pid until release_task
* is called. Odd but simple and correct.
*/
detach_pid(tsk, PIDTYPE_PID);
tsk->pid = leader->pid;
attach_pid(tsk, PIDTYPE_PID, find_pid(tsk->pid));
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);
list_replace_rcu(&leader->tasks, &tsk->tasks);
tsk->group_leader = tsk;
leader->group_leader = tsk;
tsk->exit_signal = SIGCHLD;
BUG_ON(leader->exit_state != EXIT_ZOMBIE);
leader->exit_state = EXIT_DEAD;
write_unlock_irq(&tasklist_lock);
}
/*
* There may be one thread left which is just exiting,
* but it's safe to stop telling the group to kill themselves.
*/
sig->flags = 0;
no_thread_group:
exit_itimers(sig);
if (leader)
release_task(leader);
BUG_ON(atomic_read(&sig->count) != 1);
if (atomic_read(&oldsighand->count) == 1) {
/*
* Now that we nuked the rest of the thread group,
* it turns out we are not sharing sighand any more either.
* So we can just keep it.
*/
kmem_cache_free(sighand_cachep, newsighand);
} else {
/*
* Move our state over to newsighand and switch it in.
*/
atomic_set(&newsighand->count, 1);
memcpy(newsighand->action, oldsighand->action,
sizeof(newsighand->action));
write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock);
spin_lock_nested(&newsighand->siglock, SINGLE_DEPTH_NESTING);
rcu_assign_pointer(tsk->sighand, newsighand);
recalc_sigpending();
spin_unlock(&newsighand->siglock);
spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock);
__cleanup_sighand(oldsighand);
}
BUG_ON(!thread_group_leader(tsk));
return 0;
}
/*
* These functions flushes out all traces of the currently running executable
* so that a new one can be started
*/
static void flush_old_files(struct files_struct * files)
{
long j = -1;
struct fdtable *fdt;
spin_lock(&files->file_lock);
for (;;) {
unsigned long set, i;
j++;
i = j * __NFDBITS;
fdt = files_fdtable(files);
if (i >= fdt->max_fds)
break;
set = fdt->close_on_exec->fds_bits[j];
if (!set)
continue;
fdt->close_on_exec->fds_bits[j] = 0;
spin_unlock(&files->file_lock);
for ( ; set ; i++,set >>= 1) {
if (set & 1) {
sys_close(i);
}
}
spin_lock(&files->file_lock);
}
spin_unlock(&files->file_lock);
}
void get_task_comm(char *buf, struct task_struct *tsk)
{
/* buf must be at least sizeof(tsk->comm) in size */
task_lock(tsk);
strncpy(buf, tsk->comm, sizeof(tsk->comm));
task_unlock(tsk);
}
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
}
int flush_old_exec(struct linux_binprm * bprm)
{
char * name;
int i, ch, retval;
struct files_struct *files;
char tcomm[sizeof(current->comm)];
/*
* Make sure we have a private signal table and that
* we are unassociated from the previous thread group.
*/
retval = de_thread(current);
if (retval)
goto out;
/*
* Make sure we have private file handles. Ask the
* fork helper to do the work for us and the exit
* helper to do the cleanup of the old one.
*/
files = current->files; /* refcounted so safe to hold */
retval = unshare_files();
if (retval)
goto out;
/*
* Release all of the old mmap stuff
*/
retval = exec_mmap(bprm->mm);
if (retval)
goto mmap_failed;
bprm->mm = NULL; /* We're using it now */
/* This is the point of no return */
put_files_struct(files);
current->sas_ss_sp = current->sas_ss_size = 0;
if (current->euid == current->uid && current->egid == current->gid)
set_dumpable(current->mm, 1);
else
set_dumpable(current->mm, suid_dumpable);
name = bprm->filename;
/* Copies the binary name from after last slash */
for (i=0; (ch = *(name++)) != '\0';) {
if (ch == '/')
i = 0; /* overwrite what we wrote */
else
if (i < (sizeof(tcomm) - 1))
tcomm[i++] = ch;
}
tcomm[i] = '\0';
set_task_comm(current, tcomm);
current->flags &= ~PF_RANDOMIZE;
flush_thread();
/* Set the new mm task size. We have to do that late because it may
* depend on TIF_32BIT which is only updated in flush_thread() on
* some architectures like powerpc
*/
current->mm->task_size = TASK_SIZE;
if (bprm->e_uid != current->euid || bprm->e_gid != current->egid ||
file_permission(bprm->file, MAY_READ) ||
(bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
suid_keys(current);
set_dumpable(current->mm, suid_dumpable);
}
/* An exec changes our domain. We are no longer part of the thread
group */
current->self_exec_id++;
flush_signal_handlers(current, 0);
flush_old_files(current->files);
return 0;
mmap_failed:
reset_files_struct(current, files);
out:
return retval;
}
EXPORT_SYMBOL(flush_old_exec);
/*
* Fill the binprm structure from the inode.
* Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
*/
int prepare_binprm(struct linux_binprm *bprm)
{
int mode;
struct inode * inode = bprm->file->f_path.dentry->d_inode;
int retval;
mode = inode->i_mode;
if (bprm->file->f_op == NULL)
return -EACCES;
bprm->e_uid = current->euid;
bprm->e_gid = current->egid;
if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
/* Set-uid? */
if (mode & S_ISUID) {
current->personality &= ~PER_CLEAR_ON_SETID;
bprm->e_uid = inode->i_uid;
}
/* 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)) {
current->personality &= ~PER_CLEAR_ON_SETID;
bprm->e_gid = inode->i_gid;
}
}
/* fill in binprm security blob */
retval = security_bprm_set(bprm);
if (retval)
return retval;
memset(bprm->buf,0,BINPRM_BUF_SIZE);
return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
}
EXPORT_SYMBOL(prepare_binprm);
static int unsafe_exec(struct task_struct *p)
{
int unsafe = 0;
if (p->ptrace & PT_PTRACED) {
if (p->ptrace & PT_PTRACE_CAP)
unsafe |= LSM_UNSAFE_PTRACE_CAP;
else
unsafe |= LSM_UNSAFE_PTRACE;
}
if (atomic_read(&p->fs->count) > 1 ||
atomic_read(&p->files->count) > 1 ||
atomic_read(&p->sighand->count) > 1)
unsafe |= LSM_UNSAFE_SHARE;
return unsafe;
}
void compute_creds(struct linux_binprm *bprm)
{
int unsafe;
if (bprm->e_uid != current->uid)
suid_keys(current);
exec_keys(current);
task_lock(current);
unsafe = unsafe_exec(current);
security_bprm_apply_creds(bprm, unsafe);
task_unlock(current);
security_bprm_post_apply_creds(bprm);
}
EXPORT_SYMBOL(compute_creds);
/*
* Arguments are '\0' separated strings found at the location bprm->p
* points to; chop off the first by relocating brpm->p to right after
* the first '\0' encountered.
*/
int remove_arg_zero(struct linux_binprm *bprm)
{
int ret = 0;
unsigned long offset;
char *kaddr;
struct page *page;
if (!bprm->argc)
return 0;
do {
offset = bprm->p & ~PAGE_MASK;
page = get_arg_page(bprm, bprm->p, 0);
if (!page) {
ret = -EFAULT;
goto out;
}
kaddr = kmap_atomic(page, KM_USER0);
for (; offset < PAGE_SIZE && kaddr[offset];
offset++, bprm->p++)
;
kunmap_atomic(kaddr, KM_USER0);
put_arg_page(page);
if (offset == PAGE_SIZE)
free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
} while (offset == PAGE_SIZE);
bprm->p++;
bprm->argc--;
ret = 0;
out:
return ret;
}
EXPORT_SYMBOL(remove_arg_zero);
/*
* 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;
struct linux_binfmt *fmt;
#ifdef __alpha__
/* handle /sbin/loader.. */
{
struct exec * eh = (struct exec *) bprm->buf;
if (!bprm->loader && eh->fh.f_magic == 0x183 &&
(eh->fh.f_flags & 0x3000) == 0x3000)
{
struct file * file;
unsigned long loader;
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
loader = bprm->vma->vm_end - sizeof(void *);
file = open_exec("/sbin/loader");
retval = PTR_ERR(file);
if (IS_ERR(file))
return retval;
/* Remember if the application is TASO. */
bprm->sh_bang = eh->ah.entry < 0x100000000UL;
bprm->file = file;
bprm->loader = loader;
retval = prepare_binprm(bprm);
if (retval<0)
return retval;
/* should call search_binary_handler recursively here,
but it does not matter */
}
}
#endif
retval = security_bprm_check(bprm);
if (retval)
return retval;
/* kernel module loader fixup */
/* so we don't try to load run modprobe in kernel space. */
set_fs(USER_DS);
retval = audit_bprm(bprm);
if (retval)
return retval;
retval = -ENOENT;
for (try=0; try<2; try++) {
read_lock(&binfmt_lock);
for (fmt = formats ; fmt ; fmt = fmt->next) {
int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
if (!fn)
continue;
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
retval = fn(bprm, regs);
if (retval >= 0) {
put_binfmt(fmt);
allow_write_access(bprm->file);
if (bprm->file)
fput(bprm->file);
bprm->file = NULL;
current->did_exec = 1;
proc_exec_connector(current);
return retval;
}
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (retval != -ENOEXEC || bprm->mm == NULL)
break;
if (!bprm->file) {
read_unlock(&binfmt_lock);
return retval;
}
}
read_unlock(&binfmt_lock);
if (retval != -ENOEXEC || bprm->mm == NULL) {
break;
#ifdef CONFIG_KMOD
}else{
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
if (printable(bprm->buf[0]) &&
printable(bprm->buf[1]) &&
printable(bprm->buf[2]) &&
printable(bprm->buf[3]))
break; /* -ENOEXEC */
request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
#endif
}
}
return retval;
}
EXPORT_SYMBOL(search_binary_handler);
/*
* sys_execve() executes a new program.
*/
int do_execve(char * filename,
char __user *__user *argv,
char __user *__user *envp,
struct pt_regs * regs)
{
struct linux_binprm *bprm;
struct file *file;
unsigned long env_p;
int retval;
retval = -ENOMEM;
bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
if (!bprm)
goto out_ret;
file = open_exec(filename);
retval = PTR_ERR(file);
if (IS_ERR(file))
goto out_kfree;
sched_exec();
bprm->file = file;
bprm->filename = filename;
bprm->interp = filename;
retval = bprm_mm_init(bprm);
if (retval)
goto out_file;
bprm->argc = count(argv, MAX_ARG_STRINGS);
if ((retval = bprm->argc) < 0)
goto out_mm;
bprm->envc = count(envp, MAX_ARG_STRINGS);
if ((retval = bprm->envc) < 0)
goto out_mm;
retval = security_bprm_alloc(bprm);
if (retval)
goto out;
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;
env_p = bprm->p;
retval = copy_strings(bprm->argc, argv, bprm);
if (retval < 0)
goto out;
bprm->argv_len = env_p - bprm->p;
retval = search_binary_handler(bprm,regs);
if (retval >= 0) {
/* execve success */
free_arg_pages(bprm);
security_bprm_free(bprm);
acct_update_integrals(current);
kfree(bprm);
return retval;
}
out:
free_arg_pages(bprm);
if (bprm->security)
security_bprm_free(bprm);
out_mm:
if (bprm->mm)
mmput (bprm->mm);
out_file:
if (bprm->file) {
allow_write_access(bprm->file);
fput(bprm->file);
}
out_kfree:
kfree(bprm);
out_ret:
return retval;
}
int set_binfmt(struct linux_binfmt *new)
{
struct linux_binfmt *old = current->binfmt;
if (new) {
if (!try_module_get(new->module))
return -1;
}
current->binfmt = new;
if (old)
module_put(old->module);
return 0;
}
EXPORT_SYMBOL(set_binfmt);
/* format_corename will inspect the pattern parameter, and output a
* name into corename, which must have space for at least
* CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
*/
static int format_corename(char *corename, const char *pattern, long signr)
{
const char *pat_ptr = pattern;
char *out_ptr = corename;
char *const out_end = corename + CORENAME_MAX_SIZE;
int rc;
int pid_in_pattern = 0;
int ispipe = 0;
if (*pattern == '|')
ispipe = 1;
/* Repeat as long as we have more pattern to process and more output
space */
while (*pat_ptr) {
if (*pat_ptr != '%') {
if (out_ptr == out_end)
goto out;
*out_ptr++ = *pat_ptr++;
} else {
switch (*++pat_ptr) {
case 0:
goto out;
/* Double percent, output one percent */
case '%':
if (out_ptr == out_end)
goto out;
*out_ptr++ = '%';
break;
/* pid */
case 'p':
pid_in_pattern = 1;
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", current->tgid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* uid */
case 'u':
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", current->uid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* gid */
case 'g':
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", current->gid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* signal that caused the coredump */
case 's':
rc = snprintf(out_ptr, out_end - out_ptr,
"%ld", signr);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* UNIX time of coredump */
case 't': {
struct timeval tv;
do_gettimeofday(&tv);
rc = snprintf(out_ptr, out_end - out_ptr,
"%lu", tv.tv_sec);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
}
/* hostname */
case 'h':
down_read(&uts_sem);
rc = snprintf(out_ptr, out_end - out_ptr,
"%s", utsname()->nodename);
up_read(&uts_sem);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* executable */
case 'e':
rc = snprintf(out_ptr, out_end - out_ptr,
"%s", current->comm);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
default:
break;
}
++pat_ptr;
}
}
/* Backward compatibility with core_uses_pid:
*
* If core_pattern does not include a %p (as is the default)
* and core_uses_pid is set, then .%pid will be appended to
* the filename. Do not do this for piped commands. */
if (!ispipe && !pid_in_pattern
&& (core_uses_pid || atomic_read(&current->mm->mm_users) != 1)) {
rc = snprintf(out_ptr, out_end - out_ptr,
".%d", current->tgid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
}
out:
*out_ptr = 0;
return ispipe;
}
static void zap_process(struct task_struct *start)
{
struct task_struct *t;
start->signal->flags = SIGNAL_GROUP_EXIT;
start->signal->group_stop_count = 0;
t = start;
do {
if (t != current && t->mm) {
t->mm->core_waiters++;
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
}
} while ((t = next_thread(t)) != start);
}
static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
int exit_code)
{
struct task_struct *g, *p;
unsigned long flags;
int err = -EAGAIN;
spin_lock_irq(&tsk->sighand->siglock);
if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
tsk->signal->group_exit_code = exit_code;
zap_process(tsk);
err = 0;
}
spin_unlock_irq(&tsk->sighand->siglock);
if (err)
return err;
if (atomic_read(&mm->mm_users) == mm->core_waiters + 1)
goto done;
rcu_read_lock();
for_each_process(g) {
if (g == tsk->group_leader)
continue;
p = g;
do {
if (p->mm) {
if (p->mm == mm) {
/*
* p->sighand can't disappear, but
* may be changed by de_thread()
*/
lock_task_sighand(p, &flags);
zap_process(p);
unlock_task_sighand(p, &flags);
}
break;
}
} while ((p = next_thread(p)) != g);
}
rcu_read_unlock();
done:
return mm->core_waiters;
}
static int coredump_wait(int exit_code)
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
struct completion startup_done;
struct completion *vfork_done;
int core_waiters;
init_completion(&mm->core_done);
init_completion(&startup_done);
mm->core_startup_done = &startup_done;
core_waiters = zap_threads(tsk, mm, exit_code);
up_write(&mm->mmap_sem);
if (unlikely(core_waiters < 0))
goto fail;
/*
* Make sure nobody is waiting for us to release the VM,
* otherwise we can deadlock when we wait on each other
*/
vfork_done = tsk->vfork_done;
if (vfork_done) {
tsk->vfork_done = NULL;
complete(vfork_done);
}
if (core_waiters)
wait_for_completion(&startup_done);
fail:
BUG_ON(mm->core_waiters);
return core_waiters;
}
/*
* set_dumpable converts traditional three-value dumpable to two flags and
* stores them into mm->flags. It modifies lower two bits of mm->flags, but
* these bits are not changed atomically. So get_dumpable can observe the
* intermediate state. To avoid doing unexpected behavior, get get_dumpable
* return either old dumpable or new one by paying attention to the order of
* modifying the bits.
*
* dumpable | mm->flags (binary)
* old new | initial interim final
* ---------+-----------------------
* 0 1 | 00 01 01
* 0 2 | 00 10(*) 11
* 1 0 | 01 00 00
* 1 2 | 01 11 11
* 2 0 | 11 10(*) 00
* 2 1 | 11 11 01
*
* (*) get_dumpable regards interim value of 10 as 11.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
switch (value) {
case 0:
clear_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 1:
set_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 2:
set_bit(MMF_DUMP_SECURELY, &mm->flags);
smp_wmb();
set_bit(MMF_DUMPABLE, &mm->flags);
break;
}
}
EXPORT_SYMBOL_GPL(set_dumpable);
int get_dumpable(struct mm_struct *mm)
{
int ret;
ret = mm->flags & 0x3;
return (ret >= 2) ? 2 : ret;
}
int do_coredump(long signr, int exit_code, struct pt_regs * regs)
{
char corename[CORENAME_MAX_SIZE + 1];
struct mm_struct *mm = current->mm;
struct linux_binfmt * binfmt;
struct inode * inode;
struct file * file;
int retval = 0;
int fsuid = current->fsuid;
int flag = 0;
int ispipe = 0;
audit_core_dumps(signr);
binfmt = current->binfmt;
if (!binfmt || !binfmt->core_dump)
goto fail;
down_write(&mm->mmap_sem);
if (!get_dumpable(mm)) {
up_write(&mm->mmap_sem);
goto fail;
}
/*
* We cannot trust fsuid as being the "true" uid of the
* process nor do we know its entire history. We only know it
* was tainted so we dump it as root in mode 2.
*/
if (get_dumpable(mm) == 2) { /* Setuid core dump mode */
flag = O_EXCL; /* Stop rewrite attacks */
current->fsuid = 0; /* Dump root private */
}
set_dumpable(mm, 0);
retval = coredump_wait(exit_code);
if (retval < 0)
goto fail;
/*
* Clear any false indication of pending signals that might
* be seen by the filesystem code called to write the core file.
*/
clear_thread_flag(TIF_SIGPENDING);
if (current->signal->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump)
goto fail_unlock;
/*
* lock_kernel() because format_corename() is controlled by sysctl, which
* uses lock_kernel()
*/
lock_kernel();
ispipe = format_corename(corename, core_pattern, signr);
unlock_kernel();
if (ispipe) {
/* SIGPIPE can happen, but it's just never processed */
if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) {
printk(KERN_INFO "Core dump to %s pipe failed\n",
corename);
goto fail_unlock;
}
} else
file = filp_open(corename,
O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
0600);
if (IS_ERR(file))
goto fail_unlock;
inode = file->f_path.dentry->d_inode;
if (inode->i_nlink > 1)
goto close_fail; /* multiple links - don't dump */
if (!ispipe && d_unhashed(file->f_path.dentry))
goto close_fail;
/* AK: actually i see no reason to not allow this for named pipes etc.,
but keep the previous behaviour for now. */
if (!ispipe && !S_ISREG(inode->i_mode))
goto close_fail;
if (!file->f_op)
goto close_fail;
if (!file->f_op->write)
goto close_fail;
if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
goto close_fail;
retval = binfmt->core_dump(signr, regs, file);
if (retval)
current->signal->group_exit_code |= 0x80;
close_fail:
filp_close(file, NULL);
fail_unlock:
current->fsuid = fsuid;
complete_all(&mm->core_done);
fail:
return retval;
}
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