linux-kernel - Re: [PATCH v2 RESEND] coresight: etm-perf: Fix reference count leak in etm_setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251215095103.GA681384@e132581.arm.com>
Date: Mon, 15 Dec 2025 09:51:03 +0000
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: Ma Ke <make24@...as.ac.cn>, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, stable@...r.kernel.org,
	suzuki.poulose@....com, mike.leach@...aro.org,
	alexander.shishkin@...ux.intel.com, mathieu.poirier@...aro.org
Subject: Re: [PATCH v2 RESEND] coresight: etm-perf: Fix reference count leak
 in etm_setup_aux

On Mon, Dec 15, 2025 at 11:02:08AM +0200, James Clark wrote:
> 
> 
> On 15/12/2025 04:27, Ma Ke wrote:
> > In etm_setup_aux(), when a user sink is obtained via
> > coresight_get_sink_by_id(), it increments the reference count of the
> > sink device. However, if the sink is used in path building, the path
> > holds a reference, but the initial reference from
> > coresight_get_sink_by_id() is not released, causing a reference count
> > leak. We should release the initial reference after the path is built.
> > 
> > Found by code review.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: 0e6c20517596 ("coresight: etm-perf: Allow an event to use different sinks")
> > Signed-off-by: Ma Ke <make24@...as.ac.cn>
> > ---
> > Changes in v2:
> > - modified the patch as suggestions.
> 
> I think Leo's comment on the previous v2 is still unaddressed. But releasing
> it in coresight_get_sink_by_id() would make it consistent with
> coresight_find_csdev_by_fwnode() and prevent further mistakes.

The point is the coresight core layer uses coresight_grab_device() to
increase the device's refcnt.  This is why we don't need to grab a
device when setup AUX.

> It also leads me to see that users of coresight_find_device_by_fwnode()
> should also release it, but only one out of two appears to.

Good finding!

Thanks,
Leo