linux-kernel - Re: [PATCH v1] driver core: Fix memory leak when adding SYNC_STATE

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Date:   Mon, 18 May 2020 00:48:42 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     stable <stable@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] driver core: Fix memory leak when adding
 SYNC_STATE_ONLY device links

On Sat, May 16, 2020 at 1:07 AM Saravana Kannan <saravanak@...gle.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@...r.kernel.org
> Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag")
> Signed-off-by: Saravana Kannan <saravanak@...gle.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.

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.

Thanks,
Saravana