linux-kernel - Re: [RESEND PATCH] iommu/intel: fix variable 'iommu' set but not used

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20190522141452.9105fbd041ed24eedde950b9@linux-foundation.org>
Date:   Wed, 22 May 2019 14:14:52 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Qian Cai <cai@....pw>
Cc:     jroedel@...e.de, dwmw2@...radead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] iommu/intel: fix variable 'iommu' set but not
 used

On Wed, 22 May 2019 16:36:26 -0400 Qian Cai <cai@....pw> wrote:

> The commit cf04eee8bf0e ("iommu/vt-d: Include ACPI devices in iommu=pt")
> added for_each_active_iommu() in iommu_prepare_static_identity_mapping()
> but never used the each element, i.e, "drhd->iommu".
> 
> drivers/iommu/intel-iommu.c: In function
> 'iommu_prepare_static_identity_mapping':
> drivers/iommu/intel-iommu.c:3037:22: warning: variable 'iommu' set but
> not used [-Wunused-but-set-variable]
>   struct intel_iommu *iommu;
> 
> Fixed the warning by passing "drhd->iommu" directly to
> for_each_active_iommu() which all subsequent self-assignments should be
> ignored by a compiler anyway.
> 

Yes, assigning drhd->iommu to itself seems a bit nasty.  Maybe this is
a case for __mabe_unused (with a comment explaining why), if that fixes
the warning.  Dunno.

btw, for_each_active_dev_scope() and for_each_dev_scope() should be
dragged out and shot.  Or at least, should have those single-char
identifiers changed into something meaningful so poor sods like me have
a hope of understanding the code :(