| Message ID | 20181127052318.364-4-khalid.elmously@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [SRU,Xenial,1/1] posix-timers: Sanitize overrun handling | expand |
On 2018-11-27 00:23:18, 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 > (backported from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76) > Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com> Acked-by: Tyler Hicks <tyhicks@canonical.com> See inline comments. Thanks! > --- > include/linux/posix-timers.h | 4 ++-- > kernel/time/posix-cpu-timers.c | 8 ++++---- > kernel/time/posix-timers.c | 28 ++++++++++++++++++---------- > 3 files changed, 24 insertions(+), 16 deletions(-) > > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index 907f3fd191ac..3e28a1a8d823 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -65,8 +65,8 @@ struct k_itimer { > spinlock_t it_lock; > clockid_t it_clock; /* which timer type */ > timer_t it_id; /* timer id */ > - int it_overrun; /* overrun on pending signal */ > - int it_overrun_last; /* overrun on last delivered signal */ > + s64 it_overrun; /* overrun on pending signal */ > + s64 it_overrun_last; /* overrun on last delivered signal */ > int it_requeue_pending; /* waiting to requeue this timer */ > #define REQUEUE_PENDING 1 > int it_sigev_notify; /* notify word of sigevent struct */ > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 80016b329d94..9b6015527482 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itimer *timer, > continue; > > timer->it.cpu.expires += incr; > - timer->it_overrun += 1 << i; > + timer->it_overrun += 1LL << i; > delta -= incr; > } > } > @@ -744,7 +744,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, > timer->it_requeue_pending = (timer->it_requeue_pending + 2) & > ~REQUEUE_PENDING; > timer->it_overrun_last = 0; > - timer->it_overrun = -1; > + timer->it_overrun = -1LL; You added an "LL" suffix here that wasn't in the original patch. I'm not sure if it was intentional but I also don't think it hurts anything. > > if (new_expires != 0 && !(val < new_expires)) { > /* > @@ -1100,7 +1100,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) > posix_cpu_timer_kick_nohz(); > out: > timer->it_overrun_last = timer->it_overrun; > - timer->it_overrun = -1; > + timer->it_overrun = -1LL; Same here although posix_cpu_timer_schedule() and this assignment isn't present in the current upstream kernel. > ++timer->it_requeue_pending; > } > > @@ -1305,7 +1305,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, > memset(&timer, 0, sizeof timer); > spin_lock_init(&timer.it_lock); > timer.it_clock = which_clock; > - timer.it_overrun = -1; > + timer.it_overrun = -1LL; Same here. Tyler > error = posix_cpu_timer_create(&timer); > timer.it_process = current; > if (!error) { > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index fc7c37ad90a0..d34a7f0b92fe 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -354,6 +354,16 @@ 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 schedule_next_timer(struct k_itimer *timr) > { > @@ -362,12 +372,11 @@ static void schedule_next_timer(struct k_itimer *timr) > if (timr->it.real.interval.tv64 == 0) > return; > > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, > - timer->base->get_time(), > - timr->it.real.interval); > + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), > + timr->it.real.interval); > > timr->it_overrun_last = timr->it_overrun; > - timr->it_overrun = -1; > + timr->it_overrun = -1LL; > ++timr->it_requeue_pending; > hrtimer_restart(timer); > } > @@ -396,7 +405,7 @@ void do_schedule_next_timer(struct siginfo *info) > else > schedule_next_timer(timr); > > - info->si_overrun += timr->it_overrun_last; > + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); > } > > if (timr) > @@ -491,8 +500,7 @@ 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_overrun += hrtimer_forward(timer, now, > timr->it.real.interval); > ret = HRTIMER_RESTART; > ++timr->it_requeue_pending; > @@ -633,7 +641,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock, > it_id_set = IT_ID_SET; > new_timer->it_id = (timer_t) new_timer_id; > new_timer->it_clock = which_clock; > - new_timer->it_overrun = -1; > + new_timer->it_overrun = -1LL; > > if (timer_event_spec) { > if (copy_from_user(&event, timer_event_spec, sizeof (event))) { > @@ -762,7 +770,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting) > */ > if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || > timr->it_sigev_notify == SIGEV_NONE)) > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); > + timr->it_overrun += hrtimer_forward(timer, now, iv); > > remaining = __hrtimer_expires_remaining_adjusted(timer, now); > /* Return 0 only, when the timer is expired and not pending */ > @@ -824,7 +832,7 @@ 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 > > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team
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 > (backported from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76) > Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com> > --- > include/linux/posix-timers.h | 4 ++-- > kernel/time/posix-cpu-timers.c | 8 ++++---- > kernel/time/posix-timers.c | 28 ++++++++++++++++++---------- > 3 files changed, 24 insertions(+), 16 deletions(-) > > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index 907f3fd191ac..3e28a1a8d823 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -65,8 +65,8 @@ struct k_itimer { > spinlock_t it_lock; > clockid_t it_clock; /* which timer type */ > timer_t it_id; /* timer id */ > - int it_overrun; /* overrun on pending signal */ > - int it_overrun_last; /* overrun on last delivered signal */ > + s64 it_overrun; /* overrun on pending signal */ > + s64 it_overrun_last; /* overrun on last delivered signal */ > int it_requeue_pending; /* waiting to requeue this timer */ > #define REQUEUE_PENDING 1 > int it_sigev_notify; /* notify word of sigevent struct */ > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 80016b329d94..9b6015527482 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itimer *timer, > continue; > > timer->it.cpu.expires += incr; > - timer->it_overrun += 1 << i; > + timer->it_overrun += 1LL << i; > delta -= incr; > } > } > @@ -744,7 +744,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, > timer->it_requeue_pending = (timer->it_requeue_pending + 2) & > ~REQUEUE_PENDING; > timer->it_overrun_last = 0; > - timer->it_overrun = -1; > + timer->it_overrun = -1LL; > > if (new_expires != 0 && !(val < new_expires)) { > /* > @@ -1100,7 +1100,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) > posix_cpu_timer_kick_nohz(); > out: > timer->it_overrun_last = timer->it_overrun; > - timer->it_overrun = -1; > + timer->it_overrun = -1LL; > ++timer->it_requeue_pending; > } > > @@ -1305,7 +1305,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, > memset(&timer, 0, sizeof timer); > spin_lock_init(&timer.it_lock); > timer.it_clock = which_clock; > - timer.it_overrun = -1; > + timer.it_overrun = -1LL; > error = posix_cpu_timer_create(&timer); > timer.it_process = current; > if (!error) { Same comments here as from the patch for Trusty. These changes would be nice, but I'm not sure diverting from mainline would be worth. Thanks, Kleber > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index fc7c37ad90a0..d34a7f0b92fe 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -354,6 +354,16 @@ 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 schedule_next_timer(struct k_itimer *timr) > { > @@ -362,12 +372,11 @@ static void schedule_next_timer(struct k_itimer *timr) > if (timr->it.real.interval.tv64 == 0) > return; > > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, > - timer->base->get_time(), > - timr->it.real.interval); > + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), > + timr->it.real.interval); > > timr->it_overrun_last = timr->it_overrun; > - timr->it_overrun = -1; > + timr->it_overrun = -1LL; > ++timr->it_requeue_pending; > hrtimer_restart(timer); > } > @@ -396,7 +405,7 @@ void do_schedule_next_timer(struct siginfo *info) > else > schedule_next_timer(timr); > > - info->si_overrun += timr->it_overrun_last; > + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); > } > > if (timr) > @@ -491,8 +500,7 @@ 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_overrun += hrtimer_forward(timer, now, > timr->it.real.interval); > ret = HRTIMER_RESTART; > ++timr->it_requeue_pending; > @@ -633,7 +641,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock, > it_id_set = IT_ID_SET; > new_timer->it_id = (timer_t) new_timer_id; > new_timer->it_clock = which_clock; > - new_timer->it_overrun = -1; > + new_timer->it_overrun = -1LL; > > if (timer_event_spec) { > if (copy_from_user(&event, timer_event_spec, sizeof (event))) { > @@ -762,7 +770,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting) > */ > if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || > timr->it_sigev_notify == SIGEV_NONE)) > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); > + timr->it_overrun += hrtimer_forward(timer, now, iv); > > remaining = __hrtimer_expires_remaining_adjusted(timer, now); > /* Return 0 only, when the timer is expired and not pending */ > @@ -824,7 +832,7 @@ 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;
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index 907f3fd191ac..3e28a1a8d823 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -65,8 +65,8 @@ struct k_itimer { spinlock_t it_lock; clockid_t it_clock; /* which timer type */ timer_t it_id; /* timer id */ - int it_overrun; /* overrun on pending signal */ - int it_overrun_last; /* overrun on last delivered signal */ + s64 it_overrun; /* overrun on pending signal */ + s64 it_overrun_last; /* overrun on last delivered signal */ int it_requeue_pending; /* waiting to requeue this timer */ #define REQUEUE_PENDING 1 int it_sigev_notify; /* notify word of sigevent struct */ diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 80016b329d94..9b6015527482 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itimer *timer, continue; timer->it.cpu.expires += incr; - timer->it_overrun += 1 << i; + timer->it_overrun += 1LL << i; delta -= incr; } } @@ -744,7 +744,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, timer->it_requeue_pending = (timer->it_requeue_pending + 2) & ~REQUEUE_PENDING; timer->it_overrun_last = 0; - timer->it_overrun = -1; + timer->it_overrun = -1LL; if (new_expires != 0 && !(val < new_expires)) { /* @@ -1100,7 +1100,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) posix_cpu_timer_kick_nohz(); out: timer->it_overrun_last = timer->it_overrun; - timer->it_overrun = -1; + timer->it_overrun = -1LL; ++timer->it_requeue_pending; } @@ -1305,7 +1305,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, memset(&timer, 0, sizeof timer); spin_lock_init(&timer.it_lock); timer.it_clock = which_clock; - timer.it_overrun = -1; + timer.it_overrun = -1LL; error = posix_cpu_timer_create(&timer); timer.it_process = current; if (!error) { diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index fc7c37ad90a0..d34a7f0b92fe 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -354,6 +354,16 @@ 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 schedule_next_timer(struct k_itimer *timr) { @@ -362,12 +372,11 @@ static void schedule_next_timer(struct k_itimer *timr) if (timr->it.real.interval.tv64 == 0) return; - timr->it_overrun += (unsigned int) hrtimer_forward(timer, - timer->base->get_time(), - timr->it.real.interval); + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), + timr->it.real.interval); timr->it_overrun_last = timr->it_overrun; - timr->it_overrun = -1; + timr->it_overrun = -1LL; ++timr->it_requeue_pending; hrtimer_restart(timer); } @@ -396,7 +405,7 @@ void do_schedule_next_timer(struct siginfo *info) else schedule_next_timer(timr); - info->si_overrun += timr->it_overrun_last; + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); } if (timr) @@ -491,8 +500,7 @@ 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_overrun += hrtimer_forward(timer, now, timr->it.real.interval); ret = HRTIMER_RESTART; ++timr->it_requeue_pending; @@ -633,7 +641,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock, it_id_set = IT_ID_SET; new_timer->it_id = (timer_t) new_timer_id; new_timer->it_clock = which_clock; - new_timer->it_overrun = -1; + new_timer->it_overrun = -1LL; if (timer_event_spec) { if (copy_from_user(&event, timer_event_spec, sizeof (event))) { @@ -762,7 +770,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting) */ if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || timr->it_sigev_notify == SIGEV_NONE)) - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); + timr->it_overrun += hrtimer_forward(timer, now, iv); remaining = __hrtimer_expires_remaining_adjusted(timer, now); /* Return 0 only, when the timer is expired and not pending */ @@ -824,7 +832,7 @@ 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;