| Message ID | 20181127052318.364-2-khalid.elmously@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [SRU,Bionic,1/1] posix-timers: Sanitize overrun handling | expand |
On 2018-11-27 00:23:16, Khalid Elmously wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > CVE-2018-12896 > > The posix timer overrun handling is broken because the forwarding functions > can return a huge number of overruns which does not fit in an int. As a > consequence timer_getoverrun(2) and siginfo::si_overrun can turn into > random number generators. > > The k_clock::timer_forward() callbacks return a 64 bit value now. Make > k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal > accounting is correct. 3Remove the temporary (int) casts. > > Add a helper function which clamps the overrun value returned to user space > via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value > between 0 and INT_MAX. INT_MAX is an indicator for user space that the > overrun value has been clamped. > > Reported-by: Team OWL337 <icytxw@gmail.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Acked-by: John Stultz <john.stultz@linaro.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de > (cherry picked from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76) > Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com> Acked-by: Tyler Hicks <tyhicks@canonical.com> This ack is only for the Bionic patch. Thanks! Tyler
On 11/27/18 6:23 AM, Khalid Elmously wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > CVE-2018-12896 > > The posix timer overrun handling is broken because the forwarding functions > can return a huge number of overruns which does not fit in an int. As a > consequence timer_getoverrun(2) and siginfo::si_overrun can turn into > random number generators. > > The k_clock::timer_forward() callbacks return a 64 bit value now. Make > k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal > accounting is correct. 3Remove the temporary (int) casts. > > Add a helper function which clamps the overrun value returned to user space > via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value > between 0 and INT_MAX. INT_MAX is an indicator for user space that the > overrun value has been clamped. > > Reported-by: Team OWL337 <icytxw@gmail.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Acked-by: John Stultz <john.stultz@linaro.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de > (cherry picked from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76) > Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com> Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> > --- > include/linux/posix-timers.h | 4 ++-- > kernel/time/posix-cpu-timers.c | 2 +- > kernel/time/posix-timers.c | 29 +++++++++++++++++++---------- > 3 files changed, 22 insertions(+), 13 deletions(-) > > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index 672c4f32311e..437a539898ae 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -82,8 +82,8 @@ struct k_itimer { > clockid_t it_clock; > timer_t it_id; > int it_active; > - int it_overrun; > - int it_overrun_last; > + s64 it_overrun; > + s64 it_overrun_last; > int it_requeue_pending; > int it_sigev_notify; > ktime_t it_interval; > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 1f27887aa194..0f5f019c6645 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -84,7 +84,7 @@ static void bump_cpu_timer(struct k_itimer *timer, u64 now) > continue; > > timer->it.cpu.expires += incr; > - timer->it_overrun += 1 << i; > + timer->it_overrun += 1LL << i; > delta -= incr; > } > } > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index 708992708332..3192a986a483 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -283,6 +283,17 @@ static __init int init_posix_timers(void) > } > __initcall(init_posix_timers); > > +/* > + * The siginfo si_overrun field and the return value of timer_getoverrun(2) > + * are of type int. Clamp the overrun value to INT_MAX > + */ > +static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval) > +{ > + s64 sum = timr->it_overrun_last + (s64)baseval; > + > + return sum > (s64)INT_MAX ? INT_MAX : (int)sum; > +} > + > static void common_hrtimer_rearm(struct k_itimer *timr) > { > struct hrtimer *timer = &timr->it.real.timer; > @@ -290,9 +301,8 @@ static void common_hrtimer_rearm(struct k_itimer *timr) > if (!timr->it_interval) > return; > > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, > - timer->base->get_time(), > - timr->it_interval); > + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), > + timr->it_interval); > hrtimer_restart(timer); > } > > @@ -321,10 +331,10 @@ void posixtimer_rearm(struct siginfo *info) > > timr->it_active = 1; > timr->it_overrun_last = timr->it_overrun; > - timr->it_overrun = -1; > + timr->it_overrun = -1LL; > ++timr->it_requeue_pending; > > - info->si_overrun += timr->it_overrun_last; > + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); > } > > unlock_timer(timr, flags); > @@ -418,9 +428,8 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer) > now = ktime_add(now, kj); > } > #endif > - timr->it_overrun += (unsigned int) > - hrtimer_forward(timer, now, > - timr->it_interval); > + timr->it_overrun += hrtimer_forward(timer, now, > + timr->it_interval); > ret = HRTIMER_RESTART; > ++timr->it_requeue_pending; > timr->it_active = 1; > @@ -524,7 +533,7 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, > new_timer->it_id = (timer_t) new_timer_id; > new_timer->it_clock = which_clock; > new_timer->kclock = kc; > - new_timer->it_overrun = -1; > + new_timer->it_overrun = -1LL; > > if (event) { > rcu_read_lock(); > @@ -789,7 +798,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id) > if (!timr) > return -EINVAL; > > - overrun = timr->it_overrun_last; > + overrun = timer_overrun_to_int(timr, 0); > unlock_timer(timr, flags); > > return overrun;
On 2018-11-27 00:23:16 , Khalid Elmously wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > CVE-2018-12896 > > The posix timer overrun handling is broken because the forwarding functions > can return a huge number of overruns which does not fit in an int. As a > consequence timer_getoverrun(2) and siginfo::si_overrun can turn into > random number generators. > > The k_clock::timer_forward() callbacks return a 64 bit value now. Make > k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal > accounting is correct. 3Remove the temporary (int) casts. > > Add a helper function which clamps the overrun value returned to user space > via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value > between 0 and INT_MAX. INT_MAX is an indicator for user space that the > overrun value has been clamped. > > Reported-by: Team OWL337 <icytxw@gmail.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Acked-by: John Stultz <john.stultz@linaro.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de > (cherry picked from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76) > Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com> > --- > include/linux/posix-timers.h | 4 ++-- > kernel/time/posix-cpu-timers.c | 2 +- > kernel/time/posix-timers.c | 29 +++++++++++++++++++---------- > 3 files changed, 22 insertions(+), 13 deletions(-) > > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index 672c4f32311e..437a539898ae 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -82,8 +82,8 @@ struct k_itimer { > clockid_t it_clock; > timer_t it_id; > int it_active; > - int it_overrun; > - int it_overrun_last; > + s64 it_overrun; > + s64 it_overrun_last; > int it_requeue_pending; > int it_sigev_notify; > ktime_t it_interval; > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 1f27887aa194..0f5f019c6645 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -84,7 +84,7 @@ static void bump_cpu_timer(struct k_itimer *timer, u64 now) > continue; > > timer->it.cpu.expires += incr; > - timer->it_overrun += 1 << i; > + timer->it_overrun += 1LL << i; > delta -= incr; > } > } > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index 708992708332..3192a986a483 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -283,6 +283,17 @@ static __init int init_posix_timers(void) > } > __initcall(init_posix_timers); > > +/* > + * The siginfo si_overrun field and the return value of timer_getoverrun(2) > + * are of type int. Clamp the overrun value to INT_MAX > + */ > +static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval) > +{ > + s64 sum = timr->it_overrun_last + (s64)baseval; > + > + return sum > (s64)INT_MAX ? INT_MAX : (int)sum; > +} > + > static void common_hrtimer_rearm(struct k_itimer *timr) > { > struct hrtimer *timer = &timr->it.real.timer; > @@ -290,9 +301,8 @@ static void common_hrtimer_rearm(struct k_itimer *timr) > if (!timr->it_interval) > return; > > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, > - timer->base->get_time(), > - timr->it_interval); > + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), > + timr->it_interval); > hrtimer_restart(timer); > } > > @@ -321,10 +331,10 @@ void posixtimer_rearm(struct siginfo *info) > > timr->it_active = 1; > timr->it_overrun_last = timr->it_overrun; > - timr->it_overrun = -1; > + timr->it_overrun = -1LL; > ++timr->it_requeue_pending; > > - info->si_overrun += timr->it_overrun_last; > + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); > } > > unlock_timer(timr, flags); > @@ -418,9 +428,8 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer) > now = ktime_add(now, kj); > } > #endif > - timr->it_overrun += (unsigned int) > - hrtimer_forward(timer, now, > - timr->it_interval); > + timr->it_overrun += hrtimer_forward(timer, now, > + timr->it_interval); > ret = HRTIMER_RESTART; > ++timr->it_requeue_pending; > timr->it_active = 1; > @@ -524,7 +533,7 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, > new_timer->it_id = (timer_t) new_timer_id; > new_timer->it_clock = which_clock; > new_timer->kclock = kc; > - new_timer->it_overrun = -1; > + new_timer->it_overrun = -1LL; > > if (event) { > rcu_read_lock(); > @@ -789,7 +798,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id) > if (!timr) > return -EINVAL; > > - overrun = timr->it_overrun_last; > + overrun = timer_overrun_to_int(timr, 0); > unlock_timer(timr, flags); > > return overrun; > -- > 2.17.1 >
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index 672c4f32311e..437a539898ae 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -82,8 +82,8 @@ struct k_itimer { clockid_t it_clock; timer_t it_id; int it_active; - int it_overrun; - int it_overrun_last; + s64 it_overrun; + s64 it_overrun_last; int it_requeue_pending; int it_sigev_notify; ktime_t it_interval; diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 1f27887aa194..0f5f019c6645 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -84,7 +84,7 @@ static void bump_cpu_timer(struct k_itimer *timer, u64 now) continue; timer->it.cpu.expires += incr; - timer->it_overrun += 1 << i; + timer->it_overrun += 1LL << i; delta -= incr; } } diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 708992708332..3192a986a483 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -283,6 +283,17 @@ static __init int init_posix_timers(void) } __initcall(init_posix_timers); +/* + * The siginfo si_overrun field and the return value of timer_getoverrun(2) + * are of type int. Clamp the overrun value to INT_MAX + */ +static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval) +{ + s64 sum = timr->it_overrun_last + (s64)baseval; + + return sum > (s64)INT_MAX ? INT_MAX : (int)sum; +} + static void common_hrtimer_rearm(struct k_itimer *timr) { struct hrtimer *timer = &timr->it.real.timer; @@ -290,9 +301,8 @@ static void common_hrtimer_rearm(struct k_itimer *timr) if (!timr->it_interval) return; - timr->it_overrun += (unsigned int) hrtimer_forward(timer, - timer->base->get_time(), - timr->it_interval); + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), + timr->it_interval); hrtimer_restart(timer); } @@ -321,10 +331,10 @@ void posixtimer_rearm(struct siginfo *info) timr->it_active = 1; timr->it_overrun_last = timr->it_overrun; - timr->it_overrun = -1; + timr->it_overrun = -1LL; ++timr->it_requeue_pending; - info->si_overrun += timr->it_overrun_last; + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); } unlock_timer(timr, flags); @@ -418,9 +428,8 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer) now = ktime_add(now, kj); } #endif - timr->it_overrun += (unsigned int) - hrtimer_forward(timer, now, - timr->it_interval); + timr->it_overrun += hrtimer_forward(timer, now, + timr->it_interval); ret = HRTIMER_RESTART; ++timr->it_requeue_pending; timr->it_active = 1; @@ -524,7 +533,7 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, new_timer->it_id = (timer_t) new_timer_id; new_timer->it_clock = which_clock; new_timer->kclock = kc; - new_timer->it_overrun = -1; + new_timer->it_overrun = -1LL; if (event) { rcu_read_lock(); @@ -789,7 +798,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id) if (!timr) return -EINVAL; - overrun = timr->it_overrun_last; + overrun = timer_overrun_to_int(timr, 0); unlock_timer(timr, flags); return overrun;