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

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Message-ID: <20170130190809.GH27312@n2100.armlinux.org.uk>
Date:   Mon, 30 Jan 2017 19:08:10 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Shailendra Verma <shailendra.v@...sung.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        p.shailesh@...sung.com, ashish.kalra@...sung.com,
        Shailendra Verma <shailendra.capricorn@...il.com>
Subject: Re: [PATCH] Arch: arm: plat-pxa - Fix possible NULL derefrence.

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/
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