[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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/compat.c b/fs/compat.c
index 70c5af4..a2ba78b 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1751,11 +1751,15 @@
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 @@
} 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 @@
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