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From:   Alan Mikhak <alan.mikhak@sifive.com>
To:     linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
        linux-pci@vger.kernel.org, maz@kernel.org, tglx@linutronix.de,
        gustavo.pimentel@synopsys.com, kishon@ti.com,
        paul.walmsley@sifive.com
Cc:     Alan Mikhak <alan.mikhak@sifive.com>
Subject: [PATCH] genirq/msi: Check null pointer before copying struct msi_msg
Date:   Fri, 17 Apr 2020 11:48:42 -0700
Message-Id: <1587149322-28104-1-git-send-email-alan.mikhak@sifive.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Alan Mikhak <alan.mikhak@sifive.com>

Modify __get_cached_msi_msg() to check both pointers for null before
copying the contents from the struct msi_msg pointer to the pointer
provided by caller.

Without this sanity check, __get_cached_msi_msg() crashes when invoked by
dw_edma_irq_request() in drivers/dma/dw-edma/dw-edma-core.c running on a
Linux-based PCIe endpoint device. MSI interrupt are not received by PCIe
endpoint devices. As a result, irq_get_msi_desc() returns null since there
are no cached struct msi_msg entry on the endpoint side.

Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
---
 kernel/irq/msi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index eb95f6106a1e..f39d42ef0d50 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -58,7 +58,8 @@ void free_msi_entry(struct msi_desc *entry)
 
 void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
-	*msg = entry->msg;
+	if (entry && msg)
+		*msg = entry->msg;
 }
 
 void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
-- 
2.7.4