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Subject: Re: arch/powerpc/kernel/cacheinfo.c: Possible null pointer dereference
From: Michael Ellerman <michael@ellerman.id.au>
To: David Binderman <dcb314@hotmail.com>
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Date: Mon, 14 Feb 2011 10:24:30 +1100
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On Sat, 2011-02-12 at 10:08 +0000, David Binderman wrote:
> Hello there,
>=20
> I just tried out cppcheck-1.47 on the linux-2.6.38-rc4 source code.
>=20
> It said
>=20
> [arch/powerpc/kernel/cacheinfo.c:380]: (error) Possible null pointer
> dereference: cache - otherwise it is redundant to check if cache is
> null at line 382
>=20
> The source code is
>=20
>     WARN_ONCE(cache && cache->level !=3D level,
>           "cache level mismatch on lookup (got %d, expected %d)\n",
>           cache->level, level);
>=20
>     if (!cache)
>=20
> I agree with cppcheck. Suggest code rework.

It's wrong.

The code is essentially:

if (cache && cache->level !=3D level)
	printf("cache level mismatch on lookup (got %d, expected %d)\n", cache->le=
vel, level);

if (!cache)
	cache =3D cache_do_one_devnode(node, level);


Which looks fine to me?

cheers

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