| From | Kamal Mostafa <> | Subject | [PATCH 3.13 120/160] timer: Prevent overflow in apply_slack | Date | Tue, 10 Jun 2014 12:46:00 -0700 |
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3.13.11.3 -stable review patch. If anyone has any objections, please let me know.
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From: Jiri Bohac <jbohac@suse.cz>
commit 98a01e779f3c66b0b11cd7e64d531c0e41c95762 upstream.
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> Link: http://lkml.kernel.org/r/20140418152310.GA13654@midget.suse.cz Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- kernel/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/timer.c b/kernel/timer.c index accfd24..38f0d40 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -822,7 +822,7 @@ 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); -- 1.9.1
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