| From 98a01e779f3c66b0b11cd7e64d531c0e41c95762 Mon Sep 17 00:00:00 2001 |
| From: Jiri Bohac <jbohac@suse.cz> |
| Date: Fri, 18 Apr 2014 17:23:11 +0200 |
| Subject: timer: Prevent overflow in apply_slack |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/timer.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/kernel/timer.c |
| +++ b/kernel/timer.c |
| @@ -822,7 +822,7 @@ unsigned long apply_slack(struct timer_l |
| |
| bit = find_last_bit(&mask, BITS_PER_LONG); |
| |
| - mask = (1 << bit) - 1; |
| + mask = (1UL << bit) - 1; |
| |
| expires_limit = expires_limit & ~(mask); |
| |