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| author | Ian Jackson <Ian.Jackson@eu.citrix.com> | 2012-11-14 11:33:15 +0000 |
|---|---|---|
| committer | Ian Jackson <Ian.Jackson@eu.citrix.com> | 2012-11-14 11:33:15 +0000 |
| commit | c622d6300c46b498ddc8b2e80413721a96645984 (patch) | |
| tree | 36881c7cc41fe30ad8c156cc6ef5a61a52a8b8f3 | |
| parent | a00d58bcee30c8f087aa9c58b2d9e10a1cb0de39 (diff) | |
| download | xen-c622d6300c46b498ddc8b2e80413721a96645984.tar.gz xen-c622d6300c46b498ddc8b2e80413721a96645984.tar.bz2 xen-c622d6300c46b498ddc8b2e80413721a96645984.zip | |
VCPU/timers: Prevent overflow in calculations, leading to DoS vulnerability
The timer action for a vcpu periodic timer is to calculate the next
expiry time, and to reinsert itself into the timer queue. If the
deadline ends up in the past, Xen never leaves __do_softirq(). The
affected PCPU will stay in an infinite loop until Xen is killed by the
watchdog (if enabled).
This is a security problem, XSA-20 / CVE-2012-4535.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
xen-unstable changeset: 26148:bf58b94b3cef
Backport-requested-by: security@xen.org
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
| -rw-r--r-- | xen/common/domain.c | 3 | ||||
| -rw-r--r-- | xen/include/xen/time.h | 2 |
2 files changed, 5 insertions, 0 deletions
diff --git a/xen/common/domain.c b/xen/common/domain.c index a1aa05e03b..e728819ac3 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -882,6 +882,9 @@ long do_vcpu_op(int cmd, int vcpuid, XEN_GUEST_HANDLE(void) arg) if ( set.period_ns < MILLISECS(1) ) return -EINVAL; + if ( set.period_ns > STIME_DELTA_MAX ) + return -EINVAL; + v->periodic_period = set.period_ns; vcpu_force_reschedule(v); diff --git a/xen/include/xen/time.h b/xen/include/xen/time.h index 0b2eaade3a..4224962de2 100644 --- a/xen/include/xen/time.h +++ b/xen/include/xen/time.h @@ -55,6 +55,8 @@ struct tm gmtime(unsigned long t); #define MILLISECS(_ms) ((s_time_t)((_ms) * 1000000ULL)) #define MICROSECS(_us) ((s_time_t)((_us) * 1000ULL)) #define STIME_MAX ((s_time_t)((uint64_t)~0ull>>1)) +/* Chosen so (NOW() + delta) wont overflow without an uptime of 200 years */ +#define STIME_DELTA_MAX ((s_time_t)((uint64_t)~0ull>>2)) extern void update_vcpu_system_time(struct vcpu *v); extern void update_domain_wallclock_time(struct domain *d); |