Message ID | 20200115184418.21365-1-andrew.cooper3@citrix.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | xen/vcpu: Improve sanity checks in vcpu_create() | expand |
On 15.01.2020 19:44, Andrew Cooper wrote: > The BUG_ON() is confusing to follow. The (!is_idle_domain(d) || vcpu_id) part > is a vestigial remnant of architectures poisioning idle_vcpu[0] with non-NULL > pointers. > > Now that idle_vcpu[0] is NULL on all architectures, and d->max_vcpus specified > before vcpu_create() is called, we can properly range check the requested > vcpu_id. I guess this is meant to be true on top of your Arm side change which hasn't been committed yet? And perhaps better "... starts out as NULL on all ..."? > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
Hi, On 16/01/2020 09:55, Jan Beulich wrote: > On 15.01.2020 19:44, Andrew Cooper wrote: >> The BUG_ON() is confusing to follow. The (!is_idle_domain(d) || vcpu_id) part >> is a vestigial remnant of architectures poisioning idle_vcpu[0] with non-NULL >> pointers. >> >> Now that idle_vcpu[0] is NULL on all architectures, and d->max_vcpus specified >> before vcpu_create() is called, we can properly range check the requested >> vcpu_id. > > I guess this is meant to be true on top of your Arm side change > which hasn't been committed yet? And perhaps better "... starts > out as NULL on all ..."? I can commit the two together. > >> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > > Reviewed-by: Jan Beulich <jbeulich@suse.com> Acked-by: Julien Grall <julien@xen.org> Cheers,
diff --git a/xen/common/domain.c b/xen/common/domain.c index 0b1103fdb2..ee3f9ffd3e 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -139,7 +139,19 @@ struct vcpu *vcpu_create(struct domain *d, unsigned int vcpu_id) { struct vcpu *v; - BUG_ON((!is_idle_domain(d) || vcpu_id) && d->vcpu[vcpu_id]); + /* + * Sanity check some input expectations: + * - vcpu_id should be bounded by d->max_vcpus, and not previously + * allocated. + * - VCPUs should be tightly packed and allocated in ascending order, + * except for the idle domain which may vary based on PCPU numbering. + */ + if ( vcpu_id >= d->max_vcpus || d->vcpu[vcpu_id] || + (!is_idle_domain(d) && vcpu_id && !d->vcpu[vcpu_id - 1]) ) + { + ASSERT_UNREACHABLE(); + return NULL; + } if ( (v = alloc_vcpu_struct(d)) == NULL ) return NULL;
The BUG_ON() is confusing to follow. The (!is_idle_domain(d) || vcpu_id) part is a vestigial remnant of architectures poisioning idle_vcpu[0] with non-NULL pointers. Now that idle_vcpu[0] is NULL on all architectures, and d->max_vcpus specified before vcpu_create() is called, we can properly range check the requested vcpu_id. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Wei Liu <wl@xen.org> CC: Roger Pau Monné <roger.pau@citrix.com> CC: Stefano Stabellini <sstabellini@kernel.org> CC: Julien Grall <julien@xen.org> CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com> --- xen/common/domain.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)