Re: [GIT PULL] Enable -Wstringop-overflow globally

[Gustavo A. R. Silva]

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@xxxxxxxxxxxx> 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
>
> -
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