43 lines
1.7 KiB
Diff
43 lines
1.7 KiB
Diff
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References: CVE-2012-4535 XSA-20 bnc#786516
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VCPU/timers: Prevent overflow in calculations, leading to DoS vulnerability
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The timer action for a vcpu periodic timer is to calculate the next
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expiry time, and to reinsert itself into the timer queue. If the
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deadline ends up in the past, Xen never leaves __do_softirq(). The
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affected PCPU will stay in an infinite loop until Xen is killed by the
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watchdog (if enabled).
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This is a security problem, XSA-20 / CVE-2012-4535.
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Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Acked-by: Ian Campbell <ian.campbell@citrix.com>
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Index: xen-4.2.0-testing/xen/common/domain.c
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===================================================================
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--- xen-4.2.0-testing.orig/xen/common/domain.c
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+++ xen-4.2.0-testing/xen/common/domain.c
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@@ -882,6 +882,9 @@ long do_vcpu_op(int cmd, int vcpuid, XEN
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if ( set.period_ns < MILLISECS(1) )
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return -EINVAL;
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+ if ( set.period_ns > STIME_DELTA_MAX )
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+ return -EINVAL;
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+
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v->periodic_period = set.period_ns;
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vcpu_force_reschedule(v);
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Index: xen-4.2.0-testing/xen/include/xen/time.h
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===================================================================
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--- xen-4.2.0-testing.orig/xen/include/xen/time.h
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+++ xen-4.2.0-testing/xen/include/xen/time.h
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@@ -55,6 +55,8 @@ struct tm gmtime(unsigned long t);
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#define MILLISECS(_ms) ((s_time_t)((_ms) * 1000000ULL))
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#define MICROSECS(_us) ((s_time_t)((_us) * 1000ULL))
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#define STIME_MAX ((s_time_t)((uint64_t)~0ull>>1))
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+/* Chosen so (NOW() + delta) wont overflow without an uptime of 200 years */
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+#define STIME_DELTA_MAX ((s_time_t)((uint64_t)~0ull>>2))
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extern void update_vcpu_system_time(struct vcpu *v);
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extern void update_domain_wallclock_time(struct domain *d);
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