From: Shyam Saini <mayhs11saini@gmail.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>,
iommu@lists.linux-foundation.org,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>, Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Matthew Wilcox <willy@infradead.org>,
Christopher Lameter <cl@linux.com>,
Kees Cook <keescook@chromium.org>,
clang-built-linux@googlegroups.com
Subject: Re: [PATCH] kernel: dma: Make CMA boot parameters __ro_after_init
Date: Wed, 16 Oct 2019 15:41:39 +0530 [thread overview]
Message-ID: <CAOfkYf5wagQzj0UboBdBh6iDq1ox=TN7inpatuhitw+Gsak1GQ@mail.gmail.com> (raw)
In-Reply-To: <20191014022543.GA2674@ubuntu-m2-xlarge-x86>
Hi Nathan,
On Mon, Oct 14, 2019 at 7:55 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Sat, Oct 12, 2019 at 05:59:18PM +0530, Shyam Saini wrote:
> > This parameters are not changed after early boot.
> > By making them __ro_after_init will reduce any attack surface in the
> > kernel.
> >
> > Link: https://lwn.net/Articles/676145/
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> > Cc: Robin Murphy <robin.murphy@arm.com>
> > Cc: Matthew Wilcox <willy@infradead.org>
> > Cc: Christopher Lameter <cl@linux.com>
> > Cc: Kees Cook <keescook@chromium.org>
> > Signed-off-by: Shyam Saini <mayhs11saini@gmail.com>
> > ---
> > kernel/dma/contiguous.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> > index 69cfb4345388..1b689b1303cd 100644
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -42,10 +42,10 @@ struct cma *dma_contiguous_default_area;
> > * Users, who want to set the size of global CMA area for their system
> > * should use cma= kernel parameter.
> > */
> > -static const phys_addr_t size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> > -static phys_addr_t size_cmdline = -1;
> > -static phys_addr_t base_cmdline;
> > -static phys_addr_t limit_cmdline;
> > +static const phys_addr_t __ro_after_init size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
>
> The 0day bot reported an issue with this change with clang:
>
> https://groups.google.com/d/msgid/clang-built-linux/201910140334.nhultlt8%25lkp%40intel.com
>
> kernel/dma/contiguous.c:46:36: error: 'size_cmdline' causes a section type conflict with 'size_bytes'
> static phys_addr_t __ro_after_init size_cmdline = -1;
> ^
> kernel/dma/contiguous.c:45:42: note: declared here
> static const phys_addr_t __ro_after_init size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> ^
> kernel/dma/contiguous.c:47:36: error: 'base_cmdline' causes a section type conflict with 'size_bytes'
> static phys_addr_t __ro_after_init base_cmdline;
> ^
> kernel/dma/contiguous.c:45:42: note: declared here
> static const phys_addr_t __ro_after_init size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> ^
> kernel/dma/contiguous.c:48:36: error: 'limit_cmdline' causes a section type conflict with 'size_bytes'
> static phys_addr_t __ro_after_init limit_cmdline;
> ^
> kernel/dma/contiguous.c:45:42: note: declared here
> static const phys_addr_t __ro_after_init size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> ^
> 3 errors generated.
Thanks for your feedback and reporting this error.
> The errors seem kind of cryptic at first but something that is const
> should automatically be in the read only section, this part of the
> commit seems unnecessary. Removing that part of the change fixes the error.
I have overlooked size_bytes variable
It shouldn't be const if it is declared as __ro_after_init.
I will fix and resend it.
next prev parent reply other threads:[~2019-10-16 10:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-12 12:29 [PATCH] kernel: dma: Make CMA boot parameters __ro_after_init Shyam Saini
2019-10-14 2:25 ` Nathan Chancellor
2019-10-16 10:11 ` Shyam Saini [this message]
2019-10-14 14:33 ` Robin Murphy
2019-10-19 5:37 ` Shyam Saini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAOfkYf5wagQzj0UboBdBh6iDq1ox=TN7inpatuhitw+Gsak1GQ@mail.gmail.com' \
--to=mayhs11saini@gmail.com \
--cc=cl@linux.com \
--cc=clang-built-linux@googlegroups.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=m.szyprowski@samsung.com \
--cc=natechancellor@gmail.com \
--cc=robin.murphy@arm.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).