* [PATCH] timer: prevent overflow in apply_slack @ 2014-04-17 19:42 Jiri Bohac 2014-04-17 21:46 ` Thomas Gleixner 0 siblings, 1 reply; 7+ messages in thread From: Jiri Bohac @ 2014-04-17 19:42 UTC (permalink / raw) To: Thomas Gleixner; +Cc: linux-kernel Prevent overflow in the computation of timer expiry time inside apply_slack(). Signed-off-by: Jiri Bohac <jbohac@suse.cz> Suggested-by: Deborah Townsend <dstownse@us.ibm.com> diff --git a/kernel/timer.c b/kernel/timer.c index 87bd529..4c36c91 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) bit = find_last_bit(&mask, BITS_PER_LONG); - mask = (1 << bit) - 1; + mask = (1LL << bit) - 1; expires_limit = expires_limit & ~(mask); -- Jiri Bohac <jbohac@suse.cz> SUSE Labs, SUSE CZ ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] timer: prevent overflow in apply_slack 2014-04-17 19:42 [PATCH] timer: prevent overflow in apply_slack Jiri Bohac @ 2014-04-17 21:46 ` Thomas Gleixner 2014-04-18 15:23 ` [PATCH v2] " Jiri Bohac 0 siblings, 1 reply; 7+ messages in thread From: Thomas Gleixner @ 2014-04-17 21:46 UTC (permalink / raw) To: Jiri Bohac; +Cc: linux-kernel On Thu, 17 Apr 2014, Jiri Bohac wrote: > Prevent overflow in the computation of timer expiry time inside > apply_slack(). What's the impact of this overflow? We don't want changelogs which describe what they do, we want them to describe WHY and WHAT kind of problem the patch fixes. Thanks, tglx ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] timer: prevent overflow in apply_slack 2014-04-17 21:46 ` Thomas Gleixner @ 2014-04-18 15:23 ` Jiri Bohac 2014-04-29 11:13 ` Jiri Bohac 2014-04-30 11:48 ` [tip:timers/urgent] timer: Prevent " tip-bot for Jiri Bohac 0 siblings, 2 replies; 7+ messages in thread From: Jiri Bohac @ 2014-04-18 15:23 UTC (permalink / raw) To: Thomas Gleixner; +Cc: Jiri Bohac, linux-kernel On architectures with sizeof(int) < sizeof (long), the computation of mask inside apply_slack() can be undefined if the computed bit is > 32. E.g. with: expires = 0xffffe6f5 and slack = 25, we get: expires_limit = 0x20000000e bit = 33 mask = (1 << 33) - 1 /* undefined */ On x86, mask becomes 1 and and the slack is not applied properly. On s390, mask is -1, expires is set to 0 and the timer fires immediately. Signed-off-by: Jiri Bohac <jbohac@suse.cz> Suggested-by: Deborah Townsend <dstownse@us.ibm.com> diff --git a/kernel/timer.c b/kernel/timer.c index 87bd529..4c36c91 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) bit = find_last_bit(&mask, BITS_PER_LONG); - mask = (1 << bit) - 1; + mask = (1LL << bit) - 1; expires_limit = expires_limit & ~(mask); -- -- Jiri Bohac <jbohac@suse.cz> SUSE Labs, SUSE CZ ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] timer: prevent overflow in apply_slack 2014-04-18 15:23 ` [PATCH v2] " Jiri Bohac @ 2014-04-29 11:13 ` Jiri Bohac 2014-04-29 17:22 ` Thomas Gleixner 2014-04-30 11:48 ` [tip:timers/urgent] timer: Prevent " tip-bot for Jiri Bohac 1 sibling, 1 reply; 7+ messages in thread From: Jiri Bohac @ 2014-04-29 11:13 UTC (permalink / raw) To: Thomas Gleixner; +Cc: linux-kernel Thomas, does this make sense now, with the new description? On Fri, Apr 18, 2014 at 05:23:11PM +0200, Jiri Bohac wrote: > On architectures with sizeof(int) < sizeof (long), the > computation of mask inside apply_slack() can be undefined if the > computed bit is > 32. > > E.g. with: expires = 0xffffe6f5 and slack = 25, we get: > > expires_limit = 0x20000000e > bit = 33 > mask = (1 << 33) - 1 /* undefined */ > > On x86, mask becomes 1 and and the slack is not applied properly. > On s390, mask is -1, expires is set to 0 and the timer fires immediately. > > Signed-off-by: Jiri Bohac <jbohac@suse.cz> > Suggested-by: Deborah Townsend <dstownse@us.ibm.com> > > diff --git a/kernel/timer.c b/kernel/timer.c > index 87bd529..4c36c91 100644 > --- a/kernel/timer.c > +++ b/kernel/timer.c > @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) > > bit = find_last_bit(&mask, BITS_PER_LONG); > > - mask = (1 << bit) - 1; > + mask = (1LL << bit) - 1; > > expires_limit = expires_limit & ~(mask); > Thanks, -- Jiri Bohac <jbohac@suse.cz> SUSE Labs, SUSE CZ ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] timer: prevent overflow in apply_slack 2014-04-29 11:13 ` Jiri Bohac @ 2014-04-29 17:22 ` Thomas Gleixner 2014-04-30 9:33 ` [PATCH v3] " Jiri Bohac 0 siblings, 1 reply; 7+ messages in thread From: Thomas Gleixner @ 2014-04-29 17:22 UTC (permalink / raw) To: Jiri Bohac; +Cc: linux-kernel On Tue, 29 Apr 2014, Jiri Bohac wrote: > Thomas, does this make sense now, with the new description? Yep, except > On Fri, Apr 18, 2014 at 05:23:11PM +0200, Jiri Bohac wrote: > > On architectures with sizeof(int) < sizeof (long), the > > computation of mask inside apply_slack() can be undefined if the > > computed bit is > 32. > > > > E.g. with: expires = 0xffffe6f5 and slack = 25, we get: > > > > expires_limit = 0x20000000e > > bit = 33 > > mask = (1 << 33) - 1 /* undefined */ > > > > On x86, mask becomes 1 and and the slack is not applied properly. > > On s390, mask is -1, expires is set to 0 and the timer fires immediately. > > > > Signed-off-by: Jiri Bohac <jbohac@suse.cz> > > Suggested-by: Deborah Townsend <dstownse@us.ibm.com> > > > > diff --git a/kernel/timer.c b/kernel/timer.c > > index 87bd529..4c36c91 100644 > > --- a/kernel/timer.c > > +++ b/kernel/timer.c > > @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) > > > > bit = find_last_bit(&mask, BITS_PER_LONG); > > > > - mask = (1 << bit) - 1; > > + mask = (1LL << bit) - 1; This should be 1UL, shouldn't it? > > expires_limit = expires_limit & ~(mask); > > > > Thanks, > > -- > Jiri Bohac <jbohac@suse.cz> > SUSE Labs, SUSE CZ > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v3] timer: prevent overflow in apply_slack 2014-04-29 17:22 ` Thomas Gleixner @ 2014-04-30 9:33 ` Jiri Bohac 0 siblings, 0 replies; 7+ messages in thread From: Jiri Bohac @ 2014-04-30 9:33 UTC (permalink / raw) To: Thomas Gleixner; +Cc: linux-kernel On Tue, Apr 29, 2014 at 07:22:25PM +0200, Thomas Gleixner wrote: > > > + mask = (1LL << bit) - 1; > > This should be 1UL, shouldn't it? yes, good catch, thanks! On architectures with sizeof(int) < sizeof (long), the computation of mask inside apply_slack() can be undefined if the computed bit is > 32. E.g. with: expires = 0xffffe6f5 and slack = 25, we get: expires_limit = 0x20000000e bit = 33 mask = (1 << 33) - 1 /* undefined */ On x86, mask becomes 1 and and the slack is not applied properly. On s390, mask is -1, expires is set to 0 and the timer fires immediately. Signed-off-by: Jiri Bohac <jbohac@suse.cz> Suggested-by: Deborah Townsend <dstownse@us.ibm.com> diff --git a/kernel/timer.c b/kernel/timer.c index 87bd529..4c36c91 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) bit = find_last_bit(&mask, BITS_PER_LONG); - mask = (1 << bit) - 1; + mask = (1UL << bit) - 1; expires_limit = expires_limit & ~(mask); -- Jiri Bohac <jbohac@suse.cz> SUSE Labs, SUSE CZ ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:timers/urgent] timer: Prevent overflow in apply_slack 2014-04-18 15:23 ` [PATCH v2] " Jiri Bohac 2014-04-29 11:13 ` Jiri Bohac @ 2014-04-30 11:48 ` tip-bot for Jiri Bohac 1 sibling, 0 replies; 7+ messages in thread From: tip-bot for Jiri Bohac @ 2014-04-30 11:48 UTC (permalink / raw) To: linux-tip-commits; +Cc: linux-kernel, dstownse, hpa, mingo, jbohac, tglx Commit-ID: 98a01e779f3c66b0b11cd7e64d531c0e41c95762 Gitweb: http://git.kernel.org/tip/98a01e779f3c66b0b11cd7e64d531c0e41c95762 Author: Jiri Bohac <jbohac@suse.cz> AuthorDate: Fri, 18 Apr 2014 17:23:11 +0200 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Wed, 30 Apr 2014 13:46:17 +0200 timer: Prevent overflow in apply_slack On architectures with sizeof(int) < sizeof (long), the computation of mask inside apply_slack() can be undefined if the computed bit is > 32. E.g. with: expires = 0xffffe6f5 and slack = 25, we get: expires_limit = 0x20000000e bit = 33 mask = (1 << 33) - 1 /* undefined */ On x86, mask becomes 1 and and the slack is not applied properly. On s390, mask is -1, expires is set to 0 and the timer fires immediately. Use 1UL << bit to solve that issue. Suggested-by: Deborah Townsend <dstownse@us.ibm.com> Signed-off-by: Jiri Bohac <jbohac@suse.cz> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20140418152310.GA13654@midget.suse.cz Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/timer.c b/kernel/timer.c index 87bd529..3bb01a3 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) bit = find_last_bit(&mask, BITS_PER_LONG); - mask = (1 << bit) - 1; + mask = (1UL << bit) - 1; expires_limit = expires_limit & ~(mask); ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-04-30 11:48 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2014-04-17 19:42 [PATCH] timer: prevent overflow in apply_slack Jiri Bohac 2014-04-17 21:46 ` Thomas Gleixner 2014-04-18 15:23 ` [PATCH v2] " Jiri Bohac 2014-04-29 11:13 ` Jiri Bohac 2014-04-29 17:22 ` Thomas Gleixner 2014-04-30 9:33 ` [PATCH v3] " Jiri Bohac 2014-04-30 11:48 ` [tip:timers/urgent] timer: Prevent " tip-bot for Jiri Bohac
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