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-rw-r--r--main/xen/xsa343-3.patch392
1 files changed, 392 insertions, 0 deletions
diff --git a/main/xen/xsa343-3.patch b/main/xen/xsa343-3.patch
new file mode 100644
index 0000000000..e513e308eb
--- /dev/null
+++ b/main/xen/xsa343-3.patch
@@ -0,0 +1,392 @@
+From: Jan Beulich <jbeulich@suse.com>
+Subject: evtchn: address races with evtchn_reset()
+
+Neither d->evtchn_port_ops nor max_evtchns(d) may be used in an entirely
+lock-less manner, as both may change by a racing evtchn_reset(). In the
+common case, at least one of the domain's event lock or the per-channel
+lock needs to be held. In the specific case of the inter-domain sending
+by evtchn_send() and notify_via_xen_event_channel() holding the other
+side's per-channel lock is sufficient, as the channel can't change state
+without both per-channel locks held. Without such a channel changing
+state, evtchn_reset() can't complete successfully.
+
+Lock-free accesses continue to be permitted for the shim (calling some
+otherwise internal event channel functions), as this happens while the
+domain is in effectively single-threaded mode. Special care also needs
+taking for the shim's marking of in-use ports as ECS_RESERVED (allowing
+use of such ports in the shim case is okay because switching into and
+hence also out of FIFO mode is impossihble there).
+
+As a side effect, certain operations on Xen bound event channels which
+were mistakenly permitted so far (e.g. unmask or poll) will be refused
+now.
+
+This is part of XSA-343.
+
+Reported-by: Julien Grall <jgrall@amazon.com>
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+Acked-by: Julien Grall <jgrall@amazon.com>
+---
+v9: Add arch_evtchn_is_special() to fix PV shim.
+v8: Add BUILD_BUG_ON() in evtchn_usable().
+v7: Add locking related comment ahead of struct evtchn_port_ops.
+v6: New.
+---
+TBD: I've been considering to move some of the wrappers from xen/event.h
+ into event_channel.c (or even drop them altogether), when they
+ require external locking (e.g. evtchn_port_init() or
+ evtchn_port_set_priority()). Does anyone have a strong opinion
+ either way?
+
+--- a/xen/arch/x86/irq.c
++++ b/xen/arch/x86/irq.c
+@@ -2488,14 +2488,24 @@ static void dump_irqs(unsigned char key)
+
+ for ( i = 0; i < action->nr_guests; )
+ {
++ struct evtchn *evtchn;
++ unsigned int pending = 2, masked = 2;
++
+ d = action->guest[i++];
+ pirq = domain_irq_to_pirq(d, irq);
+ info = pirq_info(d, pirq);
++ evtchn = evtchn_from_port(d, info->evtchn);
++ local_irq_disable();
++ if ( spin_trylock(&evtchn->lock) )
++ {
++ pending = evtchn_is_pending(d, evtchn);
++ masked = evtchn_is_masked(d, evtchn);
++ spin_unlock(&evtchn->lock);
++ }
++ local_irq_enable();
+ printk("d%d:%3d(%c%c%c)%c",
+- d->domain_id, pirq,
+- evtchn_port_is_pending(d, info->evtchn) ? 'P' : '-',
+- evtchn_port_is_masked(d, info->evtchn) ? 'M' : '-',
+- info->masked ? 'M' : '-',
++ d->domain_id, pirq, "-P?"[pending],
++ "-M?"[masked], info->masked ? 'M' : '-',
+ i < action->nr_guests ? ',' : '\n');
+ }
+ }
+--- a/xen/arch/x86/pv/shim.c
++++ b/xen/arch/x86/pv/shim.c
+@@ -660,8 +660,11 @@ void pv_shim_inject_evtchn(unsigned int
+ if ( port_is_valid(guest, port) )
+ {
+ struct evtchn *chn = evtchn_from_port(guest, port);
++ unsigned long flags;
+
++ spin_lock_irqsave(&chn->lock, flags);
+ evtchn_port_set_pending(guest, chn->notify_vcpu_id, chn);
++ spin_unlock_irqrestore(&chn->lock, flags);
+ }
+ }
+
+--- a/xen/common/event_2l.c
++++ b/xen/common/event_2l.c
+@@ -63,8 +63,10 @@ static void evtchn_2l_unmask(struct doma
+ }
+ }
+
+-static bool evtchn_2l_is_pending(const struct domain *d, evtchn_port_t port)
++static bool evtchn_2l_is_pending(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
++ evtchn_port_t port = evtchn->port;
+ unsigned int max_ports = BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d);
+
+ ASSERT(port < max_ports);
+@@ -72,8 +74,10 @@ static bool evtchn_2l_is_pending(const s
+ guest_test_bit(d, port, &shared_info(d, evtchn_pending)));
+ }
+
+-static bool evtchn_2l_is_masked(const struct domain *d, evtchn_port_t port)
++static bool evtchn_2l_is_masked(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
++ evtchn_port_t port = evtchn->port;
+ unsigned int max_ports = BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d);
+
+ ASSERT(port < max_ports);
+--- a/xen/common/event_channel.c
++++ b/xen/common/event_channel.c
+@@ -156,8 +156,9 @@ int evtchn_allocate_port(struct domain *
+
+ if ( port_is_valid(d, port) )
+ {
+- if ( evtchn_from_port(d, port)->state != ECS_FREE ||
+- evtchn_port_is_busy(d, port) )
++ const struct evtchn *chn = evtchn_from_port(d, port);
++
++ if ( chn->state != ECS_FREE || evtchn_is_busy(d, chn) )
+ return -EBUSY;
+ }
+ else
+@@ -774,6 +775,7 @@ void send_guest_vcpu_virq(struct vcpu *v
+ unsigned long flags;
+ int port;
+ struct domain *d;
++ struct evtchn *chn;
+
+ ASSERT(!virq_is_global(virq));
+
+@@ -784,7 +786,10 @@ void send_guest_vcpu_virq(struct vcpu *v
+ goto out;
+
+ d = v->domain;
+- evtchn_port_set_pending(d, v->vcpu_id, evtchn_from_port(d, port));
++ chn = evtchn_from_port(d, port);
++ spin_lock(&chn->lock);
++ evtchn_port_set_pending(d, v->vcpu_id, chn);
++ spin_unlock(&chn->lock);
+
+ out:
+ spin_unlock_irqrestore(&v->virq_lock, flags);
+@@ -813,7 +818,9 @@ void send_guest_global_virq(struct domai
+ goto out;
+
+ chn = evtchn_from_port(d, port);
++ spin_lock(&chn->lock);
+ evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
++ spin_unlock(&chn->lock);
+
+ out:
+ spin_unlock_irqrestore(&v->virq_lock, flags);
+@@ -823,6 +830,7 @@ void send_guest_pirq(struct domain *d, c
+ {
+ int port;
+ struct evtchn *chn;
++ unsigned long flags;
+
+ /*
+ * PV guests: It should not be possible to race with __evtchn_close(). The
+@@ -837,7 +845,9 @@ void send_guest_pirq(struct domain *d, c
+ }
+
+ chn = evtchn_from_port(d, port);
++ spin_lock_irqsave(&chn->lock, flags);
+ evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
++ spin_unlock_irqrestore(&chn->lock, flags);
+ }
+
+ static struct domain *global_virq_handlers[NR_VIRQS] __read_mostly;
+@@ -1034,12 +1044,15 @@ int evtchn_unmask(unsigned int port)
+ {
+ struct domain *d = current->domain;
+ struct evtchn *evtchn;
++ unsigned long flags;
+
+ if ( unlikely(!port_is_valid(d, port)) )
+ return -EINVAL;
+
+ evtchn = evtchn_from_port(d, port);
++ spin_lock_irqsave(&evtchn->lock, flags);
+ evtchn_port_unmask(d, evtchn);
++ spin_unlock_irqrestore(&evtchn->lock, flags);
+
+ return 0;
+ }
+@@ -1449,8 +1462,8 @@ static void domain_dump_evtchn_info(stru
+
+ printk(" %4u [%d/%d/",
+ port,
+- evtchn_port_is_pending(d, port),
+- evtchn_port_is_masked(d, port));
++ evtchn_is_pending(d, chn),
++ evtchn_is_masked(d, chn));
+ evtchn_port_print_state(d, chn);
+ printk("]: s=%d n=%d x=%d",
+ chn->state, chn->notify_vcpu_id, chn->xen_consumer);
+--- a/xen/common/event_fifo.c
++++ b/xen/common/event_fifo.c
+@@ -296,23 +296,26 @@ static void evtchn_fifo_unmask(struct do
+ evtchn_fifo_set_pending(v, evtchn);
+ }
+
+-static bool evtchn_fifo_is_pending(const struct domain *d, evtchn_port_t port)
++static bool evtchn_fifo_is_pending(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
+- const event_word_t *word = evtchn_fifo_word_from_port(d, port);
++ const event_word_t *word = evtchn_fifo_word_from_port(d, evtchn->port);
+
+ return word && guest_test_bit(d, EVTCHN_FIFO_PENDING, word);
+ }
+
+-static bool_t evtchn_fifo_is_masked(const struct domain *d, evtchn_port_t port)
++static bool_t evtchn_fifo_is_masked(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
+- const event_word_t *word = evtchn_fifo_word_from_port(d, port);
++ const event_word_t *word = evtchn_fifo_word_from_port(d, evtchn->port);
+
+ return !word || guest_test_bit(d, EVTCHN_FIFO_MASKED, word);
+ }
+
+-static bool_t evtchn_fifo_is_busy(const struct domain *d, evtchn_port_t port)
++static bool_t evtchn_fifo_is_busy(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
+- const event_word_t *word = evtchn_fifo_word_from_port(d, port);
++ const event_word_t *word = evtchn_fifo_word_from_port(d, evtchn->port);
+
+ return word && guest_test_bit(d, EVTCHN_FIFO_LINKED, word);
+ }
+--- a/xen/include/asm-x86/event.h
++++ b/xen/include/asm-x86/event.h
+@@ -47,4 +47,10 @@ static inline bool arch_virq_is_global(u
+ return true;
+ }
+
++#ifdef CONFIG_PV_SHIM
++# include <asm/pv/shim.h>
++# define arch_evtchn_is_special(chn) \
++ (pv_shim && (chn)->port && (chn)->state == ECS_RESERVED)
++#endif
++
+ #endif
+--- a/xen/include/xen/event.h
++++ b/xen/include/xen/event.h
+@@ -133,6 +133,24 @@ static inline struct evtchn *evtchn_from
+ return bucket_from_port(d, p) + (p % EVTCHNS_PER_BUCKET);
+ }
+
++/*
++ * "usable" as in "by a guest", i.e. Xen consumed channels are assumed to be
++ * taken care of separately where used for Xen's internal purposes.
++ */
++static bool evtchn_usable(const struct evtchn *evtchn)
++{
++ if ( evtchn->xen_consumer )
++ return false;
++
++#ifdef arch_evtchn_is_special
++ if ( arch_evtchn_is_special(evtchn) )
++ return true;
++#endif
++
++ BUILD_BUG_ON(ECS_FREE > ECS_RESERVED);
++ return evtchn->state > ECS_RESERVED;
++}
++
+ /* Wait on a Xen-attached event channel. */
+ #define wait_on_xen_event_channel(port, condition) \
+ do { \
+@@ -165,19 +183,24 @@ int evtchn_reset(struct domain *d);
+
+ /*
+ * Low-level event channel port ops.
++ *
++ * All hooks have to be called with a lock held which prevents the channel
++ * from changing state. This may be the domain event lock, the per-channel
++ * lock, or in the case of sending interdomain events also the other side's
++ * per-channel lock. Exceptions apply in certain cases for the PV shim.
+ */
+ struct evtchn_port_ops {
+ void (*init)(struct domain *d, struct evtchn *evtchn);
+ void (*set_pending)(struct vcpu *v, struct evtchn *evtchn);
+ void (*clear_pending)(struct domain *d, struct evtchn *evtchn);
+ void (*unmask)(struct domain *d, struct evtchn *evtchn);
+- bool (*is_pending)(const struct domain *d, evtchn_port_t port);
+- bool (*is_masked)(const struct domain *d, evtchn_port_t port);
++ bool (*is_pending)(const struct domain *d, const struct evtchn *evtchn);
++ bool (*is_masked)(const struct domain *d, const struct evtchn *evtchn);
+ /*
+ * Is the port unavailable because it's still being cleaned up
+ * after being closed?
+ */
+- bool (*is_busy)(const struct domain *d, evtchn_port_t port);
++ bool (*is_busy)(const struct domain *d, const struct evtchn *evtchn);
+ int (*set_priority)(struct domain *d, struct evtchn *evtchn,
+ unsigned int priority);
+ void (*print_state)(struct domain *d, const struct evtchn *evtchn);
+@@ -193,38 +216,67 @@ static inline void evtchn_port_set_pendi
+ unsigned int vcpu_id,
+ struct evtchn *evtchn)
+ {
+- d->evtchn_port_ops->set_pending(d->vcpu[vcpu_id], evtchn);
++ if ( evtchn_usable(evtchn) )
++ d->evtchn_port_ops->set_pending(d->vcpu[vcpu_id], evtchn);
+ }
+
+ static inline void evtchn_port_clear_pending(struct domain *d,
+ struct evtchn *evtchn)
+ {
+- d->evtchn_port_ops->clear_pending(d, evtchn);
++ if ( evtchn_usable(evtchn) )
++ d->evtchn_port_ops->clear_pending(d, evtchn);
+ }
+
+ static inline void evtchn_port_unmask(struct domain *d,
+ struct evtchn *evtchn)
+ {
+- d->evtchn_port_ops->unmask(d, evtchn);
++ if ( evtchn_usable(evtchn) )
++ d->evtchn_port_ops->unmask(d, evtchn);
+ }
+
+-static inline bool evtchn_port_is_pending(const struct domain *d,
+- evtchn_port_t port)
++static inline bool evtchn_is_pending(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
+- return d->evtchn_port_ops->is_pending(d, port);
++ return evtchn_usable(evtchn) && d->evtchn_port_ops->is_pending(d, evtchn);
+ }
+
+-static inline bool evtchn_port_is_masked(const struct domain *d,
+- evtchn_port_t port)
++static inline bool evtchn_port_is_pending(struct domain *d, evtchn_port_t port)
+ {
+- return d->evtchn_port_ops->is_masked(d, port);
++ struct evtchn *evtchn = evtchn_from_port(d, port);
++ bool rc;
++ unsigned long flags;
++
++ spin_lock_irqsave(&evtchn->lock, flags);
++ rc = evtchn_is_pending(d, evtchn);
++ spin_unlock_irqrestore(&evtchn->lock, flags);
++
++ return rc;
++}
++
++static inline bool evtchn_is_masked(const struct domain *d,
++ const struct evtchn *evtchn)
++{
++ return !evtchn_usable(evtchn) || d->evtchn_port_ops->is_masked(d, evtchn);
++}
++
++static inline bool evtchn_port_is_masked(struct domain *d, evtchn_port_t port)
++{
++ struct evtchn *evtchn = evtchn_from_port(d, port);
++ bool rc;
++ unsigned long flags;
++
++ spin_lock_irqsave(&evtchn->lock, flags);
++ rc = evtchn_is_masked(d, evtchn);
++ spin_unlock_irqrestore(&evtchn->lock, flags);
++
++ return rc;
+ }
+
+-static inline bool evtchn_port_is_busy(const struct domain *d,
+- evtchn_port_t port)
++static inline bool evtchn_is_busy(const struct domain *d,
++ const struct evtchn *evtchn)
+ {
+ return d->evtchn_port_ops->is_busy &&
+- d->evtchn_port_ops->is_busy(d, port);
++ d->evtchn_port_ops->is_busy(d, evtchn);
+ }
+
+ static inline int evtchn_port_set_priority(struct domain *d,
+@@ -233,6 +285,8 @@ static inline int evtchn_port_set_priori
+ {
+ if ( !d->evtchn_port_ops->set_priority )
+ return -ENOSYS;
++ if ( !evtchn_usable(evtchn) )
++ return -EACCES;
+ return d->evtchn_port_ops->set_priority(d, evtchn, priority);
+ }
+