linux-kernel - [PATCH v2 1/1] bus: mhi: host: Fix up null pointer access in mhi_irq

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Date:   Thu, 21 Jul 2022 10:15:54 +0800
From:   Qiang Yu <quic_qianyu@...cinc.com>
To:     <mani@...nel.org>, <quic_hemantk@...cinc.com>,
        <loic.poulain@...aro.org>, <quic_jhugo@...cinc.com>
CC:     <mhi@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_cang@...cinc.com>,
        Qiang Yu <quic_qianyu@...cinc.com>
Subject: [PATCH v2 1/1] bus: mhi: host: Fix up null pointer access in mhi_irq_handler

The irq handler for a shared IRQ ought to be prepared for running
even now it's being freed. So let's check the pointer used by
mhi_irq_handler to avoid null pointer access since it is probably
released before freeing IRQ.

Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
---
v1->v2: change dev_err to dev_dbg

 drivers/bus/mhi/host/main.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index f3aef77a..25ea1f8 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -430,12 +430,20 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
 {
 	struct mhi_event *mhi_event = dev;
 	struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
-	struct mhi_event_ctxt *er_ctxt =
-		&mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
+	struct mhi_event_ctxt *er_ctxt;
 	struct mhi_ring *ev_ring = &mhi_event->ring;
-	dma_addr_t ptr = le64_to_cpu(er_ctxt->rp);
+	dma_addr_t ptr;
 	void *dev_rp;
 
+	if (!mhi_cntrl->mhi_ctxt) {
+		dev_dbg(&mhi_cntrl->mhi_dev->dev,
+			"mhi_ctxt has been freed\n");
+		return IRQ_HANDLED;
+	}
+
+	er_ctxt = &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
+	ptr = le64_to_cpu(er_ctxt->rp);
+
 	if (!is_valid_ring_ptr(ev_ring, ptr)) {
 		dev_err(&mhi_cntrl->mhi_dev->dev,
 			"Event ring rp points outside of the event ring\n");
-- 
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