linux-kernel - [PATCH 2/2] kvm: mmu: page_track: Fix RCU list API usage

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Message-Id: <20200712131003.23271-2-madhuparnabhowmik10@gmail.com>
Date:   Sun, 12 Jul 2020 18:40:03 +0530
From:   madhuparnabhowmik10@...il.com
To:     paulmck@...nel.org, josh@...htriplett.org, joel@...lfernandes.org,
        pbonzini@...hat.com
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        kvm@...r.kernel.org, frextrite@...il.com,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH 2/2] kvm: mmu: page_track: Fix RCU list API usage

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

Use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu()
as it also checkes if the right lock is held.
Using hlist_for_each_entry_rcu() with a condition argument will not
report the cases where a SRCU protected list is traversed using
rcu_read_lock(). Hence, use hlist_for_each_entry_srcu().

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 arch/x86/kvm/mmu/page_track.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index a7bcde34d1f2..a9cd17625950 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -229,7 +229,8 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
 		return;
 
 	idx = srcu_read_lock(&head->track_srcu);
-	hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+	hlist_for_each_entry_srcu(n, &head->track_notifier_list, node,
+				srcu_read_lock_held(&head->track_srcu))
 		if (n->track_write)
 			n->track_write(vcpu, gpa, new, bytes, n);
 	srcu_read_unlock(&head->track_srcu, idx);
@@ -254,7 +255,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
 		return;
 
 	idx = srcu_read_lock(&head->track_srcu);
-	hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
+	hlist_for_each_entry_srcu(n, &head->track_notifier_list, node,
+				srcu_read_lock_held(&head->track_srcu))
 		if (n->track_flush_slot)
 			n->track_flush_slot(kvm, slot, n);
 	srcu_read_unlock(&head->track_srcu, idx);
-- 
2.17.1