linux/kernel/compat.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/kernel/compat.c
 *
 *  Kernel compatibililty routines for e.g. 32 bit syscall support
 *  on 64 bit kernels.
 *
 *  Copyright (C) 2002-2003 Stephen Rothwell, IBM Corporation
 */

#include <linux/linkage.h>
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/signal.h>
#include <linux/sched.h>	/* for MAX_SCHEDULE_TIMEOUT */
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/migrate.h>
#include <linux/posix-timers.h>
#include <linux/times.h>
#include <linux/ptrace.h>
#include <linux/gfp.h>

#include <linux/uaccess.h>

#ifdef __ARCH_WANT_SYS_SIGPROCMASK

/*
 * sys_sigprocmask SIG_SETMASK sets the first (compat) word of the
 * blocked set of signals to the supplied signal set
 */
static inline void compat_sig_setmask(sigset_t *blocked, compat_sigset_word set)
{
	memcpy(blocked->sig, &set, sizeof(set));
}

COMPAT_SYSCALL_DEFINE3(sigprocmask, int, how,
		       compat_old_sigset_t __user *, nset,
		       compat_old_sigset_t __user *, oset)
{
	old_sigset_t old_set, new_set;
	sigset_t new_blocked;

	old_set = current->blocked.sig[0];

	if (nset) {
		if (get_user(new_set, nset))
			return -EFAULT;
		new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));

		new_blocked = current->blocked;

		switch (how) {
		case SIG_BLOCK:
			sigaddsetmask(&new_blocked, new_set);
			break;
		case SIG_UNBLOCK:
			sigdelsetmask(&new_blocked, new_set);
			break;
		case SIG_SETMASK:
			compat_sig_setmask(&new_blocked, new_set);
			break;
		default:
			return -EINVAL;
		}

		set_current_blocked(&new_blocked);
	}

	if (oset) {
		if (put_user(old_set, oset))
			return -EFAULT;
	}

	return 0;
}

#endif

int put_compat_rusage(const struct rusage *r, struct compat_rusage __user *ru)
{
	struct compat_rusage r32;
	memset(&r32, 0, sizeof(r32));
	r32.ru_utime.tv_sec = r->ru_utime.tv_sec;
	r32.ru_utime.tv_usec = r->ru_utime.tv_usec;
	r32.ru_stime.tv_sec = r->ru_stime.tv_sec;
	r32.ru_stime.tv_usec = r->ru_stime.tv_usec;
	r32.ru_maxrss = r->ru_maxrss;
	r32.ru_ixrss = r->ru_ixrss;
	r32.ru_idrss = r->ru_idrss;
	r32.ru_isrss = r->ru_isrss;
	r32.ru_minflt = r->ru_minflt;
	r32.ru_majflt = r->ru_majflt;
	r32.ru_nswap = r->ru_nswap;
	r32.ru_inblock = r->ru_inblock;
	r32.ru_oublock = r->ru_oublock;
	r32.ru_msgsnd = r->ru_msgsnd;
	r32.ru_msgrcv = r->ru_msgrcv;
	r32.ru_nsignals = r->ru_nsignals;
	r32.ru_nvcsw = r->ru_nvcsw;
	r32.ru_nivcsw = r->ru_nivcsw;
	if (copy_to_user(ru, &r32, sizeof(r32)))
		return -EFAULT;
	return 0;
}

static int compat_get_user_cpu_mask(compat_ulong_t __user *user_mask_ptr,
				    unsigned len, struct cpumask *new_mask)
{
	unsigned long *k;

	if (len < cpumask_size())
		memset(new_mask, 0, cpumask_size());
	else if (len > cpumask_size())
		len = cpumask_size();

	k = cpumask_bits(new_mask);
	return compat_get_bitmap(k, user_mask_ptr, len * 8);
}

COMPAT_SYSCALL_DEFINE3(sched_setaffinity, compat_pid_t, pid,
		       unsigned int, len,
		       compat_ulong_t __user *, user_mask_ptr)
{
	cpumask_var_t new_mask;
	int retval;

	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
		return -ENOMEM;

	retval = compat_get_user_cpu_mask(user_mask_ptr, len, new_mask);
	if (retval)
		goto out;

	retval = sched_setaffinity(pid, new_mask);
out:
	free_cpumask_var(new_mask);
	return retval;
}

COMPAT_SYSCALL_DEFINE3(sched_getaffinity, compat_pid_t,  pid, unsigned int, len,
		       compat_ulong_t __user *, user_mask_ptr)
{
	int ret;
	cpumask_var_t mask;

	if ((len * BITS_PER_BYTE) < nr_cpu_ids)
		return -EINVAL;
	if (len & (sizeof(compat_ulong_t)-1))
		return -EINVAL;

	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
		return -ENOMEM;

	ret = sched_getaffinity(pid, mask);
	if (ret == 0) {
		unsigned int retlen = min(len, cpumask_size());

		if (compat_put_bitmap(user_mask_ptr, cpumask_bits(mask), retlen * 8))
			ret = -EFAULT;
		else
			ret = retlen;
	}
	free_cpumask_var(mask);

	return ret;
}

/*
 * We currently only need the following fields from the sigevent
 * structure: sigev_value, sigev_signo, sig_notify and (sometimes
 * sigev_notify_thread_id).  The others are handled in user mode.
 * We also assume that copying sigev_value.sival_int is sufficient
 * to keep all the bits of sigev_value.sival_ptr intact.
 */
int get_compat_sigevent(struct sigevent *event,
		const struct compat_sigevent __user *u_event)
{
	memset(event, 0, sizeof(*event));
	return (!access_ok(u_event, sizeof(*u_event)) ||
		__get_user(event->sigev_value.sival_int,
			&u_event->sigev_value.sival_int) ||
		__get_user(event->sigev_signo, &u_event->sigev_signo) ||
		__get_user(event->sigev_notify, &u_event->sigev_notify) ||
		__get_user(event->sigev_notify_thread_id,
			&u_event->sigev_notify_thread_id))
		? -EFAULT : 0;
}

long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask,
		       unsigned long bitmap_size)
{
	unsigned long nr_compat_longs;

	/* align bitmap up to nearest compat_long_t boundary */
	bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
	nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);

	if (!user_read_access_begin(umask, bitmap_size / 8))
		return -EFAULT;

	while (nr_compat_longs > 1) {
		compat_ulong_t l1, l2;
		unsafe_get_user(l1, umask++, Efault);
		unsafe_get_user(l2, umask++, Efault);
		*mask++ = ((unsigned long)l2 << BITS_PER_COMPAT_LONG) | l1;
		nr_compat_longs -= 2;
	}
	if (nr_compat_longs)
		unsafe_get_user(*mask, umask++, Efault);
	user_read_access_end();
	return 0;

Efault:
	user_read_access_end();
	return -EFAULT;
}

long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask,
		       unsigned long bitmap_size)
{
	unsigned long nr_compat_longs;

	/* align bitmap up to nearest compat_long_t boundary */
	bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
	nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);

	if (!user_write_access_begin(umask, bitmap_size / 8))
		return -EFAULT;

	while (nr_compat_longs > 1) {
		unsigned long m = *mask++;
		unsafe_put_user((compat_ulong_t)m, umask++, Efault);
		unsafe_put_user(m >> BITS_PER_COMPAT_LONG, umask++, Efault);
		nr_compat_longs -= 2;
	}
	if (nr_compat_longs)
		unsafe_put_user((compat_ulong_t)*mask, umask++, Efault);
	user_write_access_end();
	return 0;
Efault:
	user_write_access_end();
	return -EFAULT;
}

int
get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat)
{
#ifdef __BIG_ENDIAN
	compat_sigset_t v;
	if (copy_from_user(&v, compat, sizeof(compat_sigset_t)))
		return -EFAULT;
	switch (_NSIG_WORDS) {
	case 4: set->sig[3] = v.sig[6] | (((long)v.sig[7]) << 32 );
		fallthrough;
	case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 );
		fallthrough;
	case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 );
		fallthrough;
	case 1: set->sig[0] = v.sig[0] | (((long)v.sig[1]) << 32 );
	}
#else
	if (copy_from_user(set, compat, sizeof(compat_sigset_t)))
		return -EFAULT;
#endif
	return 0;
}
EXPORT_SYMBOL_GPL(get_compat_sigset);

/*
 * Allocate user-space memory for the duration of a single system call,
 * in order to marshall parameters inside a compat thunk.
 */
void __user *compat_alloc_user_space(unsigned long len)
{
	void __user *ptr;

	/* If len would occupy more than half of the entire compat space... */
	if (unlikely(len > (((compat_uptr_t)~0) >> 1)))
		return NULL;

	ptr = arch_compat_alloc_user_space(len);

	if (unlikely(!access_ok(ptr, len)))
		return NULL;

	return ptr;
}
EXPORT_SYMBOL_GPL(compat_alloc_user_space);