mshv: fix SRCU protection in irqfd resampler ack handler

Replace hlist_for_each_entry_rcu() with hlist_for_each_entry_srcu()
in mshv_irqfd_resampler_ack() to correctly handle SRCU-protected
linked list traversal.

The function uses SRCU (sleepable RCU) synchronization via
partition->pt_irq_srcu, but was incorrectly using the RCU variant
for list iteration. This could lead to race conditions when the
list is modified concurrently.

Also add srcu_read_lock_held() assertion as required by
hlist_for_each_entry_srcu() to ensure we're in the proper
read-side critical section.

Fixes: 621191d ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Li RongQing <[email protected]>
Reviewed-by: Anirudh Rayabharam (Microsoft) <[email protected]>
Acked-by: Stanislav Kinsburskii <[email protected]>
Signed-off-by: Wei Liu <[email protected]>

Author: lrq-max

drivers/hv/mshv_eventfd.c

@@ -87,8 +87,9 @@ static void mshv_irqfd_resampler_ack(struct mshv_irq_ack_notifier *mian)
 
 	idx = srcu_read_lock(&partition->pt_irq_srcu);
 
-	hlist_for_each_entry_rcu(irqfd, &resampler->rsmplr_irqfd_list,
-				 irqfd_resampler_hnode) {
+	hlist_for_each_entry_srcu(irqfd, &resampler->rsmplr_irqfd_list,
+				 irqfd_resampler_hnode,
+				 srcu_read_lock_held(&partition->pt_irq_srcu)) {
 		if (hv_should_clear_interrupt(irqfd->irqfd_lapic_irq.lapic_control.interrupt_type))
 			hv_call_clear_virtual_interrupt(partition->pt_id);