Subject: Re: linux-next: build warnings after merge of the kspp tree

From: Kees Cook <[email-masked]>
Date: Thu, 26 Aug 2021 20:29:01 -0700

On Thu, Aug 26, 2021 at 06:00:42PM +1000, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the kspp tree, today's linux-next build (arm
> multi_v7_defconfig) produced these warnings:
> 
> In file included from ./arch/arm/include/generated/asm/rwonce.h:1,
>                  from include/linux/compiler.h:264,
>                  from include/uapi/linux/swab.h:6,
>                  from include/linux/swab.h:5,
>                  from arch/arm/include/asm/opcodes.h:86,
>                  from arch/arm/include/asm/bug.h:7,
>                  from include/linux/bug.h:5,
>                  from include/linux/thread_info.h:13,
>                  from include/asm-generic/current.h:5,
>                  from ./arch/arm/include/generated/asm/current.h:1,
>                  from include/linux/sched.h:12,
>                  from include/linux/cgroup.h:12,
>                  from kernel/cgroup/cgroup-internal.h:5,
>                  from kernel/cgroup/cgroup.c:31:
> kernel/cgroup/cgroup.c: In function 'of_css':
> kernel/cgroup/cgroup.c:651:42: warning: array subscript '<unknown>' is outside the bounds of an interior zero-length array 'struct cgroup_subsys_state *[0]' [-Wzero-length-bounds]
>   651 |   return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);

Oh, that's cute. That's "with cgroups but no cgroup subsystems". :P I
will get this fixed.

> [...]
> Introduced by commit
> 
>   7d8aac16a0a8 ("Makefile: Enable -Wzero-length-bounds")
> 
> -- 
> Cheers,
> Stephen Rothwell

-- 
Kees Cook