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[PATCH] select: fix returned timeval

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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>
This commit is contained in:
Andrew Morton 2006-02-11 17:55:52 -08:00 committed by Linus Torvalds
parent 33042a9ff4
commit 643a654540
4 changed files with 92 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

37
fs/compat.c
View file

@ -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

32
fs/select.c
View file

@ -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

20
include/linux/compat.h
View file

@ -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 */

25
include/linux/time.h
View file

@ -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);