Unmasking a fifo event channel can result in unmasking it twice, once
directly in the kernel and once via a hypercall in case the event was
pending.
Fix that by doing the local unmask only if the event is not pending.
This is part of XSA-332.
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
}
/*
return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
}
/*
- * Clear MASKED, spinning if BUSY is set.
+ * Clear MASKED if not PENDING, spinning if BUSY is set.
+ * Return true if mask was cleared.
-static void clear_masked(volatile event_word_t *word)
+static bool clear_masked_cond(volatile event_word_t *word)
{
event_word_t new, old, w;
w = *word;
do {
{
event_word_t new, old, w;
w = *word;
do {
+ if (w & (1 << EVTCHN_FIFO_PENDING))
+ return false;
+
old = w & ~(1 << EVTCHN_FIFO_BUSY);
new = old & ~(1 << EVTCHN_FIFO_MASKED);
w = sync_cmpxchg(word, old, new);
} while (w != old);
old = w & ~(1 << EVTCHN_FIFO_BUSY);
new = old & ~(1 << EVTCHN_FIFO_MASKED);
w = sync_cmpxchg(word, old, new);
} while (w != old);
}
static void evtchn_fifo_unmask(evtchn_port_t port)
}
static void evtchn_fifo_unmask(evtchn_port_t port)
BUG_ON(!irqs_disabled());
BUG_ON(!irqs_disabled());
- clear_masked(word);
- if (evtchn_fifo_is_pending(port)) {
+ if (!clear_masked_cond(word)) {
struct evtchn_unmask unmask = { .port = port };
(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
}
struct evtchn_unmask unmask = { .port = port };
(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
}