linux-kernel - [PATCH] dmaengine: nbpfaxi: Fix memory corruption in probe()

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Message-ID: <b13c5225-7eff-448c-badc-a2c98e9bcaca@sabinyo.mountain>
Date: Tue, 1 Jul 2025 17:31:40 -0500
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Guennadi Liakhovetski <g.liakhovetski@....de>
Cc: Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] dmaengine: nbpfaxi: Fix memory corruption in probe()

The nbpf->chan[] array is allocated earlier in the nbpf_probe() function
and it has "num_channels" elements.  These three loops iterate one
element farther than they should and corrupt memory.

The changes to the second loop are more involved.  In this case, we're
copying data from the irqbuf[] array into the nbpf->chan[] array.  If
the data in irqbuf[i] is the error IRQ then we skip it, so the iterators
are not in sync.  I added a check to ensure that we don't go beyond the
end of the irqbuf[] array.  I'm pretty sure this can't happen, but it
seemed harmless to add a check.

On the other hand, after the loop has ended there is a check to ensure
that the "chan" iterator is where we expect it to be.  In the original
code we went one element beyond the end of the array so the iterator
wasn't in the correct place and it would always return -EINVAL.  However,
now it will always be in the correct place.  I deleted the check since
we know the result.

Cc: stable@...r.kernel.org
Fixes: b45b262cefd5 ("dmaengine: add a driver for AMBA AXI NBPF DMAC IP cores")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
>From static analysis.  Not tested.

 drivers/dma/nbpfaxi.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/nbpfaxi.c b/drivers/dma/nbpfaxi.c
index 0d6324c4e2be..7a2488a0d6a3 100644
--- a/drivers/dma/nbpfaxi.c
+++ b/drivers/dma/nbpfaxi.c
@@ -1351,7 +1351,7 @@ static int nbpf_probe(struct platform_device *pdev)
 	if (irqs == 1) {
 		eirq = irqbuf[0];

-		for (i = 0; i <= num_channels; i++)
+		for (i = 0; i < num_channels; i++)
 			nbpf->chan[i].irq = irqbuf[0];
 	} else {
 		eirq = platform_get_irq_byname(pdev, "error");
@@ -1361,16 +1361,15 @@ static int nbpf_probe(struct platform_device *pdev)
 		if (irqs == num_channels + 1) {
 			struct nbpf_channel *chan;

-			for (i = 0, chan = nbpf->chan; i <= num_channels;
+			for (i = 0, chan = nbpf->chan; i < num_channels;
 			     i++, chan++) {
 				/* Skip the error IRQ */
 				if (irqbuf[i] == eirq)
 					i++;
+				if (i >= ARRAY_SIZE(irqbuf))
+					return -EINVAL;
 				chan->irq = irqbuf[i];
 			}
-
-			if (chan != nbpf->chan + num_channels)
-				return -EINVAL;
 		} else {
 			/* 2 IRQs and more than one channel */
 			if (irqbuf[0] == eirq)
@@ -1378,7 +1377,7 @@ static int nbpf_probe(struct platform_device *pdev)
 			else
 				irq = irqbuf[0];

-			for (i = 0; i <= num_channels; i++)
+			for (i = 0; i < num_channels; i++)
 				nbpf->chan[i].irq = irq;
 		}
 	}
-- 
2.47.2