Each sgx_mmun_notifier_release() starts a grace period, which means that
one extra synchronize_rcu() in sgx_encl_release(). Add it there.
sgx_release() has the loop that drains the list but with bad luck the
entry is already gone from the list before that loop processes it.
Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer")
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reported-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/encl.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index ee50a5010277..48539a6ee315 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -438,6 +438,13 @@ void sgx_encl_release(struct kref *ref)
if (encl->backing)
fput(encl->backing);
+ /*
+ * Each sgx_mmun_notifier_release() starts a grace period. Thus one
+ * "extra" synchronize_rcu() is required here. This can go undetected by
+ * sgx_release() when it drains the mm list.
+ */
+ synchronize_srcu(&encl->srcu);
+
cleanup_srcu_struct(&encl->srcu);
WARN_ON_ONCE(!list_empty(&encl->mm_list));
--
2.27.0
