Re: [PATCH v3] coresight: ETR: Fix ETR buffer use-after-free issue

[Suzuki K Poulose]

Hi Mike

On 06/11/2025 14:14, Mike Leach wrote:
> Hi,
>
> Is this fixing the correct problem? If we prevent the buffer size from
> being changed while the sink is active - which is probably what we
> should do anyway as no real good can come from allowing this - then
> the problem disappears.

Good point. But this is completely fine for a running "sysfs" session,
as the values are not updated (unlike perf, where the session is
scheduled out and put back in ). So, I don't see why we can't change
the values while the sink is active ?


> Changing the buffer size while the sink is active should return -EBUSY;
>
> Mike
>
> On Wed, 5 Nov 2025 at 16:13, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > On Tue, 21 Oct 2025 16:45:25 +0800, Xiaoqi Zhuang wrote:
> > > When ETR is enabled as CS_MODE_SYSFS, if the buffer size is changed
> > > and enabled again, currently sysfs_buf will point to the newly
> > > allocated memory(buf_new) and free the old memory(buf_old). But the
> > > etr_buf that is being used by the ETR remains pointed to buf_old, not
> > > updated to buf_new. In this case, it will result in a memory
> > > use-after-free issue.
> > >
> > > [...]
> >
> > Applied, thanks!
> >
> > [1/1] coresight: ETR: Fix ETR buffer use-after-free issue
> >        https://git.kernel.org/coresight/c/35501ac3c7d4
> >
> > Best regards,
> > --
> > Suzuki K Poulose <suzuki.poulose@xxxxxxx>