From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Xie Bo <xb@ultrarisc.com>,
	Anup Patel <anup@brainfault.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18.y 2/2] RISC-V: KVM: Serialize IMSIC attributes with vCPU migration
Date: Wed, 30 Sep 2026 07:44:12 -0400
Message-ID: <20260930114412.1342046-2-sashal@kernel.org>
In-Reply-To: <20260930114412.1342046-1-sashal@kernel.org>
References: <2026092914-nifty-tackling-3b69@gregkh>
 <20260930114412.1342046-1-sashal@kernel.org>
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From: Xie Bo <xb@ultrarisc.com>

[ Upstream commit 8ae12ccaec6ec74945d8c1ef39f2c1b8df779abc ]

KVM device ioctls are not serialized against KVM_RUN. As a result,
kvm_riscv_aia_imsic_rw_attr() can snapshot the physical CPU and HGEI of
an IMSIC VS-file before a concurrent vCPU migration releases it.

The HGEI can then be allocated to another vCPU before imsic_vsfile_rw()
uses the stale tuple. A GET or SET attribute may consequently access the
new owner's interrupt file.

Serialize the entire IMSIC attribute operation with the target vCPU
mutex. This prevents the VS-file from being migrated and recycled until
the attribute access completes. Acquire the mutex killably so that the
device ioctl remains interruptible while waiting for KVM_RUN to finish.

Fixes: db8b7e97d613 ("RISC-V: KVM: Add in-kernel virtualization of AIA IMSIC")
Cc: stable@vger.kernel.org
Signed-off-by: Xie Bo <xb@ultrarisc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260810-imsic-attr-race-v2-1-00ed95ad321e@ultrarisc.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/riscv/kvm/aia_imsic.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c
index 0579c02ab02d6..a357ea73516f6 100644
--- a/arch/riscv/kvm/aia_imsic.c
+++ b/arch/riscv/kvm/aia_imsic.c
@@ -952,9 +952,14 @@ int kvm_riscv_aia_imsic_rw_attr(struct kvm *kvm, unsigned long type,
 	if (!vcpu)
 		return -ENODEV;
 
+	if (mutex_lock_killable(&vcpu->mutex))
+		return -EINTR;
+
 	imsic = vcpu->arch.aia_context.imsic_state;
-	if (!imsic)
-		return -ENODEV;
+	if (!imsic) {
+		rc = -ENODEV;
+		goto out_unlock;
+	}
 	isel = KVM_DEV_RISCV_AIA_IMSIC_GET_ISEL(type);
 
 	read_lock_irqsave(&imsic->vsfile_lock, flags);
@@ -978,6 +983,8 @@ int kvm_riscv_aia_imsic_rw_attr(struct kvm *kvm, unsigned long type,
 		rc = imsic_vsfile_rw(vsfile_hgei, vsfile_cpu, imsic->nr_eix,
 				     isel, write, val);
 
+out_unlock:
+	mutex_unlock(&vcpu->mutex);
 	return rc;
 }
 
-- 
2.53.0