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[PATCH] Arch: arm: plat-pxa - Fix possible NULL derefrence.

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  [PATCH] Arch: arm: plat-pxa - Fix possible NULL derefrence. Shailendra Verma <shailendra.v@samsung.com> - 2017-01-30 06:00 +0100
    Re: [PATCH] Arch: arm: plat-pxa - Fix possible NULL derefrence. Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-01-30 20:10 +0100

#1569387 — [PATCH] Arch: arm: plat-pxa - Fix possible NULL derefrence.

of_match_device could return NULL, and so can cause a NULL
pointer dereference later.

Signed-off-by: Shailendra Verma <shailendra.v@samsung.com>
---
 arch/arm/plat-pxa/ssp.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/plat-pxa/ssp.c b/arch/arm/plat-pxa/ssp.c
index ba13f79..7d1cd51 100644
--- a/arch/arm/plat-pxa/ssp.c
+++ b/arch/arm/plat-pxa/ssp.c
@@ -204,6 +204,10 @@ static int pxa_ssp_probe(struct platform_device *pdev)
 	if (dev->of_node) {
 		const struct of_device_id *id =
 			of_match_device(of_match_ptr(pxa_ssp_of_ids), dev);
+		if (!id) {
+			dev_err(dev, "Error: No device match found\n");
+			return -ENODEV;
+		}
 		ssp->type = (int) id->data;
 	} else {
 		const struct platform_device_id *id =
-- 
1.7.9.5

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#1570037

On Mon, Jan 30, 2017 at 10:28:31AM +0530, Shailendra Verma wrote:
> of_match_device could return NULL, and so can cause a NULL
> pointer dereference later.

Please explain how this can happen.

The driver is matched to the device via the driver model looking up
the compatible string in the match table:

                .of_match_table = of_match_ptr(pxa_ssp_of_ids),

It then calls the probe function, which notices that there's a DT
node pointer, and the driver looks the device up in the very same
table.

If the driver model found a match and then the device driver didn't
for the very same device, something really bad went wrong.

So, if you want to add something:

	if (WARN_ON(!id))
		return -ENODEV;

should be about it, since it's something we expect to never encounter.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

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