Commit 643a6545 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

[PATCH] select: fix returned timeval 



With David Woodhouse <dwmw2@infradead.org>

select() presently has a habit of increasing the value of the user's
`timeout' argument on return.

We were writing back a timeout larger than the original.  We _deliberately_
round up, since we know we must wait at _least_ as long as the caller asks
us to.

The patch adds a couple of helper functions for magnitude comparison of
timespecs and of timevals, and uses them to prevent the various poll and
select functions from returning a timeout which is larger than the one which
was passed in.

The patch also fixes a bug in compat_sys_pselect7(): it was adding the new
timeout value to the old one and was returning that.  It should just return
the new timeout value.

(We have various handy timespec/timeval-to-from-nsec conversion functions in
time.h.  But this code open-codes it all).

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <ak@muc.de>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: george anzinger <george@mvista.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 33042a9f

fs/compat.c

+25 −12
Original line number Diff line number Diff line
@@ -1751,11 +1751,15 @@ asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp, 
	ret = compat_core_sys_select(n, inp, outp, exp, &timeout);



	if (tvp) {

		struct compat_timeval rtv;



		if (current->personality & STICKY_TIMEOUTS)

			goto sticky;

		tv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));

		tv.tv_sec = timeout;

		if (copy_to_user(tvp, &tv, sizeof(tv))) {

		rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));

		rtv.tv_sec = timeout;

		if (compat_timeval_compare(&rtv, &tv) < 0)

			rtv = tv;

		if (copy_to_user(tvp, &rtv, sizeof(rtv))) {

sticky:

			/*

			 * If an application puts its timeval in read-only
@@ -1822,13 +1826,17 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp, 
	} while (!ret && !timeout && tsp && (ts.tv_sec || ts.tv_nsec));



	if (tsp && !(current->personality & STICKY_TIMEOUTS)) {

		ts.tv_sec += timeout / HZ;

		ts.tv_nsec += (timeout % HZ) * (1000000000/HZ);

		if (ts.tv_nsec >= 1000000000) {

			ts.tv_sec++;

			ts.tv_nsec -= 1000000000;

		struct compat_timespec rts;



		rts.tv_sec = timeout / HZ;

		rts.tv_nsec = (timeout % HZ) * (NSEC_PER_SEC/HZ);

		if (rts.tv_nsec >= NSEC_PER_SEC) {

			rts.tv_sec++;

			rts.tv_nsec -= NSEC_PER_SEC;

		}

		(void)copy_to_user(tsp, &ts, sizeof(ts));

		if (compat_timespec_compare(&rts, &ts) < 0)

			rts = ts;

		copy_to_user(tsp, &rts, sizeof(rts));

	}



	if (ret == -ERESTARTNOHAND) {
@@ -1918,12 +1926,17 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds, 
		sigprocmask(SIG_SETMASK, &sigsaved, NULL);



	if (tsp && timeout >= 0) {

		struct compat_timespec rts;



		if (current->personality & STICKY_TIMEOUTS)

			goto sticky;

		/* Yes, we know it's actually an s64, but it's also positive. */

		ts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) * 1000;

		ts.tv_sec = timeout;

		if (copy_to_user(tsp, &ts, sizeof(ts))) {

		rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *

					1000;

		rts.tv_sec = timeout;

		if (compat_timespec_compare(&rts, &ts) < 0)

			rts = ts;

		if (copy_to_user(tsp, &rts, sizeof(rts))) {

sticky:

			/*

			 * If an application puts its timeval in read-only

fs/select.c

+23 −9
Original line number Diff line number Diff line
@@ -398,11 +398,15 @@ asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp, 
	ret = core_sys_select(n, inp, outp, exp, &timeout);



	if (tvp) {

		struct timeval rtv;



		if (current->personality & STICKY_TIMEOUTS)

			goto sticky;

		tv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));

		tv.tv_sec = timeout;

		if (copy_to_user(tvp, &tv, sizeof(tv))) {

		rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));

		rtv.tv_sec = timeout;

		if (timeval_compare(&rtv, &tv) < 0)

			rtv = tv;

		if (copy_to_user(tvp, &rtv, sizeof(rtv))) {

sticky:

			/*

			 * If an application puts its timeval in read-only
@@ -460,11 +464,16 @@ asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp, 
	ret = core_sys_select(n, inp, outp, exp, &timeout);



	if (tsp) {

		struct timespec rts;



		if (current->personality & STICKY_TIMEOUTS)

			goto sticky;

		ts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) * 1000;

		ts.tv_sec = timeout;

		if (copy_to_user(tsp, &ts, sizeof(ts))) {

		rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *

						1000;

		rts.tv_sec = timeout;

		if (timespec_compare(&rts, &ts) < 0)

			rts = ts;

		if (copy_to_user(tsp, &rts, sizeof(rts))) {

sticky:

			/*

			 * If an application puts its timeval in read-only
@@ -758,12 +767,17 @@ asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds, 
		sigprocmask(SIG_SETMASK, &sigsaved, NULL);



	if (tsp && timeout >= 0) {

		struct timespec rts;



		if (current->personality & STICKY_TIMEOUTS)

			goto sticky;

		/* Yes, we know it's actually an s64, but it's also positive. */

		ts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) * 1000;

		ts.tv_sec = timeout;

		if (copy_to_user(tsp, &ts, sizeof(ts))) {

		rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *

						1000;

		rts.tv_sec = timeout;

		if (timespec_compare(&rts, &ts) < 0)

			rts = ts;

		if (copy_to_user(tsp, &rts, sizeof(rts))) {

		sticky:

			/*

			 * If an application puts its timeval in read-only

include/linux/compat.h

+20 −0
Original line number Diff line number Diff line
@@ -161,5 +161,25 @@ int copy_siginfo_to_user32(struct compat_siginfo __user *to, siginfo_t *from); 
int get_compat_sigevent(struct sigevent *event,

		const struct compat_sigevent __user *u_event);



static inline int compat_timeval_compare(struct compat_timeval *lhs,

					struct compat_timeval *rhs)

{

	if (lhs->tv_sec < rhs->tv_sec)

		return -1;

	if (lhs->tv_sec > rhs->tv_sec)

		return 1;

	return lhs->tv_usec - rhs->tv_usec;

}



static inline int compat_timespec_compare(struct compat_timespec *lhs,

					struct compat_timespec *rhs)

{

	if (lhs->tv_sec < rhs->tv_sec)

		return -1;

	if (lhs->tv_sec > rhs->tv_sec)

		return 1;

	return lhs->tv_nsec - rhs->tv_nsec;

}



#endif /* CONFIG_COMPAT */

#endif /* _LINUX_COMPAT_H */

include/linux/time.h

+24 −1
Original line number Diff line number Diff line
@@ -33,11 +33,34 @@ struct timezone { 
#define NSEC_PER_SEC		1000000000L

#define NSEC_PER_USEC		1000L



static __inline__ int timespec_equal(struct timespec *a, struct timespec *b)

static inline int timespec_equal(struct timespec *a, struct timespec *b)

{

	return (a->tv_sec == b->tv_sec) && (a->tv_nsec == b->tv_nsec);

}



/*

 * lhs < rhs:  return <0

 * lhs == rhs: return 0

 * lhs > rhs:  return >0

 */

static inline int timespec_compare(struct timespec *lhs, struct timespec *rhs)

{

	if (lhs->tv_sec < rhs->tv_sec)

		return -1;

	if (lhs->tv_sec > rhs->tv_sec)

		return 1;

	return lhs->tv_nsec - rhs->tv_nsec;

}



static inline int timeval_compare(struct timeval *lhs, struct timeval *rhs)

{

	if (lhs->tv_sec < rhs->tv_sec)

		return -1;

	if (lhs->tv_sec > rhs->tv_sec)

		return 1;

	return lhs->tv_usec - rhs->tv_usec;

}



extern unsigned long mktime(const unsigned int year, const unsigned int mon,

			    const unsigned int day, const unsigned int hour,

			    const unsigned int min, const unsigned int sec);

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