[PATCH] genirq/msi: Check null pointer before copying struct msi_msg

[Alan Mikhak]

From: Alan Mikhak <alan.mikhak@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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