From: Krzysztof Kozlowski <krzk@kernel.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Colin King <colin.king@canonical.com>,
Roger Quadros <rogerq@kernel.org>,
Tony Lindgren <tony@atomide.com>,
linux-omap@vger.kernel.org, kernel-janitors@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] memory: gpmc: fix out of bounds read and dereference on gpmc_cs[]
Date: Wed, 24 Feb 2021 09:11:04 +0100 [thread overview]
Message-ID: <20210224081104.rw6amjl6p5so5cq7@kozik-lap> (raw)
In-Reply-To: <20210224075552.GS2087@kadam>
On Wed, Feb 24, 2021 at 10:55:52AM +0300, Dan Carpenter wrote:
> On Tue, Feb 23, 2021 at 07:38:21PM +0000, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> >
> > Currently the array gpmc_cs is indexed by cs before it cs is range checked
> > and the pointer read from this out-of-index read is dereferenced. Fix this
> > by performing the range check on cs before the read and the following
> > pointer dereference.
> >
> > Addresses-Coverity: ("Negative array index read")
> > Fixes: 186401937927 ("memory: gpmc: Move omap gpmc code to live under drivers")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> > drivers/memory/omap-gpmc.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> > index cfa730cfd145..f80c2ea39ca4 100644
> > --- a/drivers/memory/omap-gpmc.c
> > +++ b/drivers/memory/omap-gpmc.c
> > @@ -1009,8 +1009,8 @@ EXPORT_SYMBOL(gpmc_cs_request);
> >
> > void gpmc_cs_free(int cs)
> > {
> > - struct gpmc_cs_data *gpmc = &gpmc_cs[cs];
> > - struct resource *res = &gpmc->mem;
>
> There is no actual dereferencing going on here, it just taking the
> addresses. But the patch is also harmless and improves readability.
Hm, in the second line indeed the compiler will just calculate the
offset of "mem" field against the "gpmc_cs+cs" and return it's probable
address.
To me still the code is a little bit non-obvious or obfuscated - first
you play with the array[index] and then you check the validity of index.
Best regards,
Krzysztof
next prev parent reply other threads:[~2021-02-24 8:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 19:38 [PATCH] memory: gpmc: fix out of bounds read and dereference on gpmc_cs[] Colin King
2021-02-23 19:52 ` Krzysztof Kozlowski
2021-02-24 7:55 ` Dan Carpenter
2021-02-24 8:11 ` Krzysztof Kozlowski [this message]
2021-02-25 12:37 ` Tony Lindgren
2021-02-24 8:46 ` Colin Ian King
2021-03-02 8:44 ` Krzysztof Kozlowski
2021-03-02 8:54 ` Colin Ian King
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=20210224081104.rw6amjl6p5so5cq7@kozik-lap \
--to=krzk@kernel.org \
--cc=colin.king@canonical.com \
--cc=dan.carpenter@oracle.com \
--cc=kernel-janitors@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-omap@vger.kernel.org \
--cc=rogerq@kernel.org \
--cc=tony@atomide.com \
/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).