From: Badhri Jagan Sridharan <badhri@google.com>
To: Peter Chen <peter.chen@freescale.com>
Cc: Felipe Balbi <balbi@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: gadget: Check for NULL pointer in disconnect
Date: Mon, 23 Mar 2015 16:00:37 -0700 [thread overview]
Message-ID: <55109B15.9080800@google.com> (raw)
In-Reply-To: <20150322074353.GA25278@shlinux2>
> Do you really see some udc drivers call it after composite_unbind is
> called? If it is, you may add dump_stack() to track that error.
>
> Besides this, function suspended_show is needed to add cdev NULL pointer
> checking.
We see this happening occasionally in *not yet* upstreamed UDC
code of some vendors (Yes, disconnect being called after unbind)
After reviewing the entire composite.c file, I did notice that
none of the functions check for NULL pointer when cdev is
obtained from get_gadget_data.
Is crashing/bringing down the whole kernel intentionally
left to happen ? Isn't printing a WARN/ERROR msg and
returning not the preferable approach ?
On 03/22/2015 12:43 AM, Peter Chen wrote:
> On Fri, Mar 20, 2015 at 04:40:52PM -0700, Badhri Jagan Sridharan wrote:
>> Added a safety net to make sure that
>> composite_disconnect does not end up disconneting
>> a NULL device. Prevents NULL pointer crash.
>>
>> Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
>> ---
>> drivers/usb/gadget/composite.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
>> index 13adfd1..90b37bd 100644
>> --- a/drivers/usb/gadget/composite.c
>> +++ b/drivers/usb/gadget/composite.c
>> @@ -1823,6 +1823,11 @@ void composite_disconnect(struct usb_gadget *gadget)
>> struct usb_composite_dev *cdev = get_gadget_data(gadget);
>> unsigned long flags;
>>
>> + if (!cdev) {
>> + WARN(1, "Trying to disconnect a NULL composite device\n");
>> + return;
>> + }
>> +
>
> Do you really see some udc drivers call it after composite_unbind is
> called? If it is, you may add dump_stack() to track that error.
>
> Besides this, function suspended_show is needed to add cdev NULL pointer
> checking.
>
>> /* REVISIT: should we have config and device level
>> * disconnect callbacks?
>> */
>> --
>> 2.2.0.rc0.207.ga3a616c
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-usb" 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:[~2015-03-23 23:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-20 23:40 [PATCH] usb: gadget: Check for NULL pointer in disconnect Badhri Jagan Sridharan
2015-03-22 7:43 ` Peter Chen
2015-03-23 23:00 ` Badhri Jagan Sridharan [this message]
2015-03-24 8:39 ` Peter Chen
2015-03-24 16:30 ` Felipe Balbi
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=55109B15.9080800@google.com \
--to=badhri@google.com \
--cc=balbi@ti.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=peter.chen@freescale.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.