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Date: Wed, 20 Mar 2024 16:33:02 +0000
From: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
To: Julia Lawall <julia.lawall@inria.fr>,
 Dan Carpenter <dan.carpenter@linaro.org>
CC: Jakub Kicinski <kuba@kernel.org>,
 Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
 Jesse Brandeburg <jesse.brandeburg@intel.com>,
 Tony Nguyen <anthony.l.nguyen@intel.com>,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Paolo Abeni <pabeni@redhat.com>,
 Przemek Kitszel <przemyslaw.kitszel@intel.com>,
 intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
 Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers
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On 20 March 2024 07:32:17 GMT, Julia Lawall <julia=2Elawall@inria=2Efr> wr=
ote:
>
>
>On Wed, 20 Mar 2024, Dan Carpenter wrote:
>
>> On Tue, Mar 19, 2024 at 12:43:17PM -0700, Jakub Kicinski wrote:
>> > On Sat, 16 Mar 2024 12:44:40 +0300 Dan Carpenter wrote:
>> > > -	struct ice_aqc_get_phy_caps_data *pcaps __free(kfree);
>> > > -	void *mac_buf __free(kfree);
>> > > +	struct ice_aqc_get_phy_caps_data *pcaps __free(kfree) =3D NULL;
>> > > +	void *mac_buf __free(kfree) =3D NULL;
>> >
>> > This is just trading one kind of bug for another, and the __free()
>> > magic is at a cost of readability=2E
>> >
>> > I think we should ban the use of __free() in all of networking,
>> > until / unless it cleanly handles the NULL init case=2E
>>
>> Free handles the NULL init case, it doesn't handle the uninitialized
>> case=2E  I had previously argued that checkpatch should complain about
>> every __free() pointer if the declaration doesn't have an assignment=2E
>>
>> The =3D NULL assignment is unnecessary if the pointer is assigned to
>> something else before the first return, so this might cause "unused
>> assignment" warnings?  I don't know if there are any tools which
>> complain about that in that situation=2E  I think probably we should ju=
st
>> make that an exception and do the checkpatch thing because it's such a
>> simple rule to implement=2E
>
>My understanding from Jonathan Cameron was that Linus wants a NULL always=
,
>unless there is an initialization with the declaration=2E

I don't have thread to hand but Linus strongly preferred moving any declar=
ation using this to
 where it is assigned so that it was obvious that the allocator and freer =
match=2E

Not checked if that makes sense here though=20
>
>julia