Commit message: compat: fix 4-byte infoleak via uninitialized struct field

Commit 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to
native counterparts") removed the memset() in compat_get_timex().  Since
then, the compat adjtimex syscall can invoke do_adjtimex() with an
uninitialized ->tai.

If do_adjtimex() doesn't write to ->tai (e.g.  because the arguments are
invalid), compat_put_timex() then copies the uninitialized ->tai field
to userspace.

Fix it by adding the memset() back.

Fixes: 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to native counterparts")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2018-11508
CWE: CWE-200
Vulnerability description: The compat_get_timex function in kernel/compat.c in the Linux kernel before 4.16.9 allows local users to obtain sensitive information from kernel memory via adjtimex.

Project: linux
File: compat.c

static int __compat_get_timespec(struct timespec *ts, const struct compat_timespec __user *cts)
{
	return (!access_ok(VERIFY_READ, cts, sizeof(*cts)) ||
			__get_user(ts->tv_sec, &cts->tv_sec) ||
			__get_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
}

Project: linux
File: compat.c

static int __compat_get_timespec64(struct timespec64 *ts64,
				   const struct compat_timespec __user *cts)
{
	struct compat_timespec ts;
	int ret;

	ret = copy_from_user(&ts, cts, sizeof(ts));
	if (ret)
		return -EFAULT;

	ts64->tv_sec = ts.tv_sec;
	ts64->tv_nsec = ts.tv_nsec;

	return 0;
}

Project: linux
File: compat.c

static int __compat_get_timeval(struct timeval *tv, const struct compat_timeval __user *ctv)
{
	return (!access_ok(VERIFY_READ, ctv, sizeof(*ctv)) ||
			__get_user(tv->tv_sec, &ctv->tv_sec) ||
			__get_user(tv->tv_usec, &ctv->tv_usec)) ? -EFAULT : 0;
}

Project: linux
File: compat.c

static int __compat_put_timespec(const struct timespec *ts, struct compat_timespec __user *cts)
{
	return (!access_ok(VERIFY_WRITE, cts, sizeof(*cts)) ||
			__put_user(ts->tv_sec, &cts->tv_sec) ||
			__put_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
}

Project: linux
File: compat.c

static int __compat_put_timespec64(const struct timespec64 *ts64,
				   struct compat_timespec __user *cts)
{
	struct compat_timespec ts = {
		.tv_sec = ts64->tv_sec,
		.tv_nsec = ts64->tv_nsec
	};
	return copy_to_user(cts, &ts, sizeof(ts)) ? -EFAULT : 0;
}

Project: linux
File: compat.c

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(VERIFY_WRITE, ptr, len)))
		return NULL;

	return ptr;
}

Project: linux
File: compat.c

int compat_get_timespec(struct timespec *ts, const void __user *uts)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
	else
		return __compat_get_timespec(ts, uts);
}

Project: linux
File: compat.c

int compat_get_timespec64(struct timespec64 *ts, const void __user *uts)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
	else
		return __compat_get_timespec64(ts, uts);
}

Project: linux
File: compat.c

int compat_get_timeval(struct timeval *tv, const void __user *utv)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_from_user(tv, utv, sizeof(*tv)) ? -EFAULT : 0;
	else
		return __compat_get_timeval(tv, utv);
}

Project: linux
File: compat.c

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);
}

Project: linux
File: compat.c

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 (!access_ok(VERIFY_WRITE, umask, bitmap_size / 8))
		return -EFAULT;

	user_access_begin();
	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_access_end();
	return 0;
Efault:
	user_access_end();
	return -EFAULT;
}

Project: linux
File: compat.c

int compat_put_timespec(const struct timespec *ts, void __user *uts)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
	else
		return __compat_put_timespec(ts, uts);
}

Project: linux
File: compat.c

int compat_put_timespec64(const struct timespec64 *ts, void __user *uts)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
	else
		return __compat_put_timespec64(ts, uts);
}

Project: linux
File: compat.c

int compat_put_timeval(const struct timeval *tv, void __user *utv)
{
	if (COMPAT_USE_64BIT_TIME)
		return copy_to_user(utv, tv, sizeof(*tv)) ? -EFAULT : 0;
	else
		return __compat_put_timeval(tv, utv);
}

Project: linux
File: compat.c

int compat_put_timex(struct compat_timex __user *utp, const struct timex *txc)
{
	struct compat_timex tx32;

	memset(&tx32, 0, sizeof(struct compat_timex));
	tx32.modes = txc->modes;
	tx32.offset = txc->offset;
	tx32.freq = txc->freq;
	tx32.maxerror = txc->maxerror;
	tx32.esterror = txc->esterror;
	tx32.status = txc->status;
	tx32.constant = txc->constant;
	tx32.precision = txc->precision;
	tx32.tolerance = txc->tolerance;
	tx32.time.tv_sec = txc->time.tv_sec;
	tx32.time.tv_usec = txc->time.tv_usec;
	tx32.tick = txc->tick;
	tx32.ppsfreq = txc->ppsfreq;
	tx32.jitter = txc->jitter;
	tx32.shift = txc->shift;
	tx32.stabil = txc->stabil;
	tx32.jitcnt = txc->jitcnt;
	tx32.calcnt = txc->calcnt;
	tx32.errcnt = txc->errcnt;
	tx32.stbcnt = txc->stbcnt;
	tx32.tai = txc->tai;
	if (copy_to_user(utp, &tx32, sizeof(struct compat_timex)))
		return -EFAULT;
	return 0;
}

Project: linux
File: compat.c

static inline void compat_sig_setmask(sigset_t *blocked, compat_sigset_word set)
{
	memcpy(blocked->sig, &set, sizeof(set));
}

Project: linux
File: compat.c

int get_compat_itimerspec64(struct itimerspec64 *its,
			const struct compat_itimerspec __user *uits)
{

	if (__compat_get_timespec64(&its->it_interval, &uits->it_interval) ||
	    __compat_get_timespec64(&its->it_value, &uits->it_value))
		return -EFAULT;
	return 0;
}

Project: linux
File: compat.c

int get_compat_itimerval(struct itimerval *o, const struct compat_itimerval __user *i)
{
	struct compat_itimerval v32;

	if (copy_from_user(&v32, i, sizeof(struct compat_itimerval)))
		return -EFAULT;
	o->it_interval.tv_sec = v32.it_interval.tv_sec;
	o->it_interval.tv_usec = v32.it_interval.tv_usec;
	o->it_value.tv_sec = v32.it_value.tv_sec;
	o->it_value.tv_usec = v32.it_value.tv_usec;
	return 0;
}

Project: linux
File: compat.c

int get_compat_sigevent(struct sigevent *event,
		const struct compat_sigevent __user *u_event)
{
	memset(event, 0, sizeof(*event));
	return (!access_ok(VERIFY_READ, 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;
}

Project: linux
File: compat.c

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 );
	case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 );
	case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 );
	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;
}

Project: linux
File: compat.c

int put_compat_itimerspec64(const struct itimerspec64 *its,
			struct compat_itimerspec __user *uits)
{
	if (__compat_put_timespec64(&its->it_interval, &uits->it_interval) ||
	    __compat_put_timespec64(&its->it_value, &uits->it_value))
		return -EFAULT;
	return 0;
}

Project: linux
File: compat.c

int put_compat_itimerval(struct compat_itimerval __user *o, const struct itimerval *i)
{
	struct compat_itimerval v32;

	v32.it_interval.tv_sec = i->it_interval.tv_sec;
	v32.it_interval.tv_usec = i->it_interval.tv_usec;
	v32.it_value.tv_sec = i->it_value.tv_sec;
	v32.it_value.tv_usec = i->it_value.tv_usec;
	return copy_to_user(o, &v32, sizeof(struct compat_itimerval)) ? -EFAULT : 0;
}

Project: linux
File: compat.c

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;
}