dmaengine: dw-edma: Check MSI descriptor before copying

Modify dw_edma_irq_request() to check if a struct msi_desc entry exists
before copying the contents of its struct msi_msg pointer.

Without this sanity check, __get_cached_msi_msg() crashes when invoked by
dw_edma_irq_request() running on a Linux-based PCIe endpoint device. MSI
interrupt are not received by PCIe endpoint devices. If irq_get_msi_desc()
returns null, then there is no cached struct msi_msg to be copied.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Link: https://lore.kernel.org/r/1587607101-31914-1-git-send-email-alan.mikhak@sifive.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/dw-edma/dw-edma-core.c

@@ -13,6 +13,7 @@
 #include <linux/dmaengine.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/dma/edma.h>
 #include <linux/dma-mapping.h>
 
@@ -773,6 +774,7 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 	u32 rd_mask = 1;
 	int i, err = 0;
 	u32 ch_cnt;
+	int irq;
 
 	ch_cnt = dw->wr_ch_cnt + dw->rd_ch_cnt;
 
@@ -781,16 +783,16 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 
 	if (dw->nr_irqs == 1) {
 		/* Common IRQ shared among all channels */
-		err = request_irq(dw->ops->irq_vector(dev, 0),
-				  dw_edma_interrupt_common,
+		irq = dw->ops->irq_vector(dev, 0);
+		err = request_irq(irq, dw_edma_interrupt_common,
 				  IRQF_SHARED, dw->name, &dw->irq[0]);
 		if (err) {
 			dw->nr_irqs = 0;
 			return err;
 		}
 
-		get_cached_msi_msg(dw->ops->irq_vector(dev, 0),
-				   &dw->irq[0].msi);
+		if (irq_get_msi_desc(irq))
+			get_cached_msi_msg(irq, &dw->irq[0].msi);
 	} else {
 		/* Distribute IRQs equally among all channels */
 		int tmp = dw->nr_irqs;
@@ -804,7 +806,8 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 		dw_edma_add_irq_mask(&rd_mask, *rd_alloc, dw->rd_ch_cnt);
 
 		for (i = 0; i < (*wr_alloc + *rd_alloc); i++) {
-			err = request_irq(dw->ops->irq_vector(dev, i),
+			irq = dw->ops->irq_vector(dev, i);
+			err = request_irq(irq,
 					  i < *wr_alloc ?
 						dw_edma_interrupt_write :
 						dw_edma_interrupt_read,
@@ -815,8 +818,8 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 				return err;
 			}
 
-			get_cached_msi_msg(dw->ops->irq_vector(dev, i),
-					   &dw->irq[i].msi);
+			if (irq_get_msi_desc(irq))
+				get_cached_msi_msg(irq, &dw->irq[i].msi);
 		}
 
 		dw->nr_irqs = i;