Received-SPF: pass (google.com: domain of linux-kernel+bounces-41383-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <0c4cc1a7-f409-4597-b110-81f9e45d1ffe@embeddedor.com>
Date: Sat, 27 Jan 2024 13:53:00 -0600
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [GIT PULL] Enable -Wstringop-overflow globally
Content-Language: en-US
To: David Laight <David.Laight@ACULAB.COM>,
 'Linus Torvalds' <torvalds@linux-foundation.org>,
 Kees Cook <keescook@chromium.org>, Lucas De Marchi
 <lucas.demarchi@intel.com>, Oded Gabbay <ogabbay@kernel.org>,
 =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= <thomas.hellstrom@linux.intel.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
 "linux-hardening@vger.kernel.org" <linux-hardening@vger.kernel.org>,
 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
 intel-xe@lists.freedesktop.org,
 "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>
References: <Za6JwRpknVIlfhPF@work>
 <CAHk-=wjG4jdE19-vWWhAX3ByfbNr4DJS-pwiN9oY38WkhMZ57g@mail.gmail.com>
 <4907a7a3-8533-480a-bc3c-488573e18e66@embeddedor.com>
 <202401261423.7AF702239@keescook>
 <CAHk-=wiaaCatzmF6GXxP97pa8oEX7e4rBpd4JgsbKex3Ek1_9A@mail.gmail.com>
 <f00e15fcba05497a87e91182a33c888f@AcuMS.aculab.com>
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
In-Reply-To: <f00e15fcba05497a87e91182a33c888f@AcuMS.aculab.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit


On 1/27/24 09:11, David Laight wrote:
> From: Linus Torvalds
>> Sent: 26 January 2024 22:36
>>
>> On Fri, 26 Jan 2024 at 14:24, Kees Cook <keescook@chromium.org> wrote:
>>>
>>> I think xe has some other weird problems too. This may be related (under
>>> allocating):
>>>
>>> ../drivers/gpu/drm/xe/xe_vm.c: In function 'xe_vma_create':
>>> ../drivers/gpu/drm/xe/xe_vm.c:806:21: warning: allocation of insufficient size '224' for type
>> 'struct xe_vma' with size '368' [-Walloc-size]
>>>    806 |                 vma = kzalloc(sizeof(*vma) - sizeof(struct xe_userptr),
>>>        |                     ^
>>
>> That code is indeed odd, but there's a comment in the xe_vma definition
>>
>>          /**
>>           * @userptr: user pointer state, only allocated for VMAs that are
>>           * user pointers
>>           */
>>          struct xe_userptr userptr;
>>
>> although I agree that it should probably simply be made a final
>> variably-sized array instead (and then you make that array size be
>> 0/1).
> 
> That entire code is odd.
> It isn't obvious that the flag values that cause the short allocate
> are the same ones that control whether the extra data is accessed.
> 
> Never mind the oddities with the 'flags |= ' assignments int the
> 'remap next' path.
> 
> Anyone know how many of these actually get allocated (and their
> lifetimes)?
> How much difference would it make to allocate 368 (maybe 384?)
> bytes instead of 224 (likely 256).

[CC+ xen list and maintainers]

Probably the xen maintainer can help us out here.

--
Gustavo

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)