From 5a7780e725d1bb4c3094fcc12f1c5c5faea1e988 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 13 Feb 2008 09:20:43 +0100
Subject: [PATCH] hrtimer: check relative timeouts for overflow
Various user space callers ask for relative timeouts. While we fixed
that overflow issue in hrtimer_start(), the sites which convert
relative user space values to absolute timeouts themself were uncovered.
Instead of putting overflow checks into each place add a function
which does the sanity checking and convert all affected callers to use
it.
Thanks to Frans Pop, who reported the problem and tested the fixes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Frans Pop <elendil@planet.nl>
---
include/linux/ktime.h | 2 ++
kernel/futex.c | 2 +-
kernel/futex_compat.c | 2 +-
kernel/hrtimer.c | 37 ++++++++++++++++++++-----------------
kernel/posix-timers.c | 8 +++++---
5 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index 36c542b70c6d..2cd7fa73d1af 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -310,6 +310,8 @@ static inline ktime_t ktime_sub_us(const ktime_t kt, const u64 usec)
return ktime_sub_ns(kt, usec * 1000);
}
+extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);
+
/*
* The resolution of the clocks. The resolution value is returned in
* the clock_getres() system call to give application programmers an
diff --git a/kernel/futex.c b/kernel/futex.c
index a6baaec44b8f..221f2128a437 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2116,7 +2116,7 @@ asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
t = timespec_to_ktime(ts);
if (cmd == FUTEX_WAIT)
- t = ktime_add(ktime_get(), t);
+ t = ktime_add_safe(ktime_get(), t);
tp = &t;
}
/*
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 133d558db452..7d5e4b016f39 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -176,7 +176,7 @@ asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
t = timespec_to_ktime(ts);
if (cmd == FUTEX_WAIT)
- t = ktime_add(ktime_get(), t);
+ t = ktime_add_safe(ktime_get(), t);
tp = &t;
}
if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 3f4a57c7895d..c2893af9479e 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -325,6 +325,23 @@ u64 ktime_divns(const ktime_t kt, s64 div)
}
#endif /* BITS_PER_LONG >= 64 */
+/*
+ * Add two ktime values and do a safety check for overflow:
+ */
+ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
+{
+ ktime_t res = ktime_add(lhs, rhs);
+
+ /*
+ * We use KTIME_SEC_MAX here, the maximum timeout which we can
+ * return to user space in a timespec:
+ */
+ if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)
+ res = ktime_set(KTIME_SEC_MAX, 0);
+
+ return res;
+}
+
/*
* Check, whether the timer is on the callback pending list
*/
@@ -682,13 +699,7 @@ u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
*/
orun++;
}
- timer->expires = ktime_add(timer->expires, interval);
- /*
- * Make sure, that the result did not wrap with a very large
- * interval.
- */
- if (timer->expires.tv64 < 0)
- timer->expires = ktime_set(KTIME_SEC_MAX, 0);
+ timer->expires = ktime_add_safe(timer->expires, interval);
return orun;
}
@@ -839,7 +850,7 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
new_base = switch_hrtimer_base(timer, base);
if (mode == HRTIMER_MODE_REL) {
- tim = ktime_add(tim, new_base->get_time());
+ tim = ktime_add_safe(tim, new_base->get_time());
/*
* CONFIG_TIME_LOW_RES is a temporary way for architectures
* to signal that they simply return xtime in
@@ -848,16 +859,8 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
* timeouts. This will go away with the GTOD framework.
*/
#ifdef CONFIG_TIME_LOW_RES
- tim = ktime_add(tim, base->resolution);
+ tim = ktime_add_safe(tim, base->resolution);
#endif
- /*
- * Careful here: User space might have asked for a
- * very long sleep, so the add above might result in a
- * negative number, which enqueues the timer in front
- * of the queue.
- */
- if (tim.tv64 < 0)
- tim.tv64 = KTIME_MAX;
}
timer->expires = tim;
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 022c9c3cee6f..a9b04203a66d 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -767,9 +767,11 @@ common_timer_set(struct k_itimer *timr, int flags,
/* SIGEV_NONE timers are not queued ! See common_timer_get */
if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {
/* Setup correct expiry time for relative timers */
- if (mode == HRTIMER_MODE_REL)
- timer->expires = ktime_add(timer->expires,
- timer->base->get_time());
+ if (mode == HRTIMER_MODE_REL) {
+ timer->expires =
+ ktime_add_safe(timer->expires,
+ timer->base->get_time());
+ }
return 0;
}