From: "Daniel Glöckner" <dg@emlix.com>
To: Dan Carpenter <error27@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jani Nikula <ext-jani.1.nikula@nokia.com>,
David Brownell <dbrownell@users.sourceforge.net>,
Andi Kleen <ak@linux.intel.com>,
linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [patch] gpio: potential null dereference
Date: Tue, 27 Apr 2010 09:41:16 +0000 [thread overview]
Message-ID: <4BD6B13C.6020406@emlix.com> (raw)
In-Reply-To: <20100427090533.GZ29093@bicker>
On 04/27/2010 11:05 AM, Dan Carpenter wrote:
> On Tue, Apr 27, 2010 at 01:05:15AM +0200, Daniel Glöckner wrote:
>> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
>>> Smatch found a potential null dereference in gpio_setup_irq(). The
>>> "pdesc" variable is allocated with idr_find() that can return NULL. If
>>> gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
>>> would OOPs here.
>> idr_find() doesn't allocate, idr_get_new_above() does.
>> Assuming idr_find() never fails for an id if idr_get_new_above()
>> successfully allocated that id, I don't think we can reach that
>> line with pdesc being NULL:
>>
>> - There are two gotos leading to free_sd
>> - #2 is after a block that allocates pdesc
>> - #1 is in an if (!gpio_flags) block
>> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) = gpio_flags)
>> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
>> - Trigger flags are added to desc->flags only after we have
>> successfully allocated pdesc (i.e. right before return 0)
>> - We start off with no trigger flags set
>>
>
> Are you sure? If we know that the call to idr_find() returns a valid
> pointer we could remove a lot of error handling code...
It returns a valid pointer iff (desc->flags & GPIO_TRIGGER_MASK).
When !(desc->flags & GPIO_TRIGGER_MASK) it returns NULL and everything
gets allocated (unless !gpio_flags as well). What you wanted to remove
is the allocation code, not error handling code. It is always run when
the trigger is set from "none" to something else.
Daniel
--
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführer: Dr. Uwe Kracke, Ust-IdNr.: DE 205 198 055
emlix - your embedded linux partner
--
To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2010-04-27 9:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-26 19:25 [patch] gpio: potential null dereference Dan Carpenter
2010-04-26 23:05 ` Daniel Glöckner
2010-04-26 23:14 ` Andrew Morton
2010-04-27 9:05 ` Dan Carpenter
2010-04-27 9:41 ` Daniel Glöckner [this message]
2010-04-27 10:30 ` Dan Carpenter
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=4BD6B13C.6020406@emlix.com \
--to=dg@emlix.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=dbrownell@users.sourceforge.net \
--cc=error27@gmail.com \
--cc=ext-jani.1.nikula@nokia.com \
--cc=kernel-janitors@vger.kernel.org \
--cc=linux-kernel@vger.kernel.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).