Re: [PATCH v1] driver core: Fix memory leak when adding SYNC_STATE_ONLY device links - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Saravana Kannan <saravanak@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	stable <stable@vger.kernel.org>,
	Android Kernel Team <kernel-team@android.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1] driver core: Fix memory leak when adding SYNC_STATE_ONLY device links
Date: Mon, 18 May 2020 10:03:27 +0200	[thread overview]
Message-ID: <20200518080327.GA3126260@kroah.com> (raw)
In-Reply-To: <CAGETcx8Ro_tsmYEQwzZKsm2xzimw=MBcChbSW5Nx9arUni53wQ@mail.gmail.com>

On Mon, May 18, 2020 at 12:48:42AM -0700, Saravana Kannan wrote:
> On Sat, May 16, 2020 at 1:07 AM Saravana Kannan <saravanak@google.com> wrote:
> >
> > When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("driver
> > core: Add device link support for SYNC_STATE_ONLY flag"),
> > device_link_add() incorrectly skipped adding the new SYNC_STATE_ONLY
> > device link to the supplier's and consumer's "device link" list. So the
> > "device link" is lost forever from driver core if the caller didn't keep
> > track of it (typically isn't expected to).
> >
> > If the same SYNC_STATE_ONLY device link is created again using
> > device_link_add(), instead of returning the pointer to the previously
> > created device link, a new device link is created and returned. This can
> > cause memory leaks in conjunction with fw_devlinks.
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag")
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
> 
> Greg/Rafael,
> 
> This patch causes a warning for SYNC_STATE_ONLY links because they
> allow consumers to probe before suppliers but the device link
> status/state change code wasn't written with that possibility in mind.
> So I need to fix up that warning or state change code.

What type of warning happens?

> Depending on how urgent you think memory leak fixes are, you can take
> it as is for now and I can send a separate patch to fix the
> warning/state change code later. Or if we can sit on this memory leak
> for a week, I might be able to fix the warning before then.

memory leaks are not ok, but neither is adding runtime warnings.  Any
chance we can't just get a fix for both?  :)

thanks,

greg k-h