linux-kernel - RE: [char-misc v2] mei: trace: treat reg parameter as string

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Message-ID: <CY5PR11MB63661D10CC4A2170274AB779ED85A@CY5PR11MB6366.namprd11.prod.outlook.com>
Date: Thu, 8 Jan 2026 12:35:51 +0000
From: "Usyskin, Alexander" <alexander.usyskin@...el.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: "Abliyev, Reuven" <reuven.abliyev@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [char-misc v2] mei: trace: treat reg parameter as string

> Subject: Re: [char-misc v2] mei: trace: treat reg parameter as string
> 
> On Thu, Jan 08, 2026 at 09:17:12AM +0100, Greg Kroah-Hartman wrote:
> > On Thu, Jan 08, 2026 at 07:59:08AM +0000, Usyskin, Alexander wrote:
> > > > Subject: Re: [char-misc v2] mei: trace: treat reg parameter as string
> > > >
> > > > On Thu, Jan 08, 2026 at 07:42:22AM +0000, Usyskin, Alexander wrote:
> > > > > > Subject: Re: [char-misc v2] mei: trace: treat reg parameter as string
> > > > > >
> > > > > > On Thu, Jan 08, 2026 at 08:57:02AM +0200, Alexander Usyskin wrote:
> > > > > > > Use the string wrapper to check sanity of the reg parameters,
> > > > > > > store it value independently and prevent internal kernel data leaks.
> > > > > > > Trace subsystem refuses to emit event with plain char*,
> > > > > > > without the wrapper.
> > > > > > >
> > > > > > > Cc: stable@...r.kernel.org
> > > > > >
> > > > > > Does this really fix a bug?  If not, there's no need for cc: stable or:
> > > > > >
> > > > > > > Fixes: a0a927d06d79 ("mei: me: add io register tracing")
> > > > > >
> > > > > > That line as well.
> > > > > >
> > > > > > thanks,
> > > > > >
> > > > > > greg k-h
> > > > >
> > > > > Without this patch the events are not emitted at all, they are dropped
> > > > > by trace security checker.
> > > >
> > > > Ah, again, that was not obvious at all from the changelog.  Perhaps
> > > > reword it a bit?  How has this ever worked?
> > > >
> > >
> > > This security hardening was introduced way after the initial commit
> > > and the breakage went unnoticed for some time, unfortunately.
> >
> > So then the "Fixes:" tag is not correct :(
> 
> Wait, no, it is, but you need to say why this is now needed, and was not
> a problem back then.  And is this really ok to backport all the way to
> that commit id, or should it just be relegated to the one where the
> "hardening" feature was added?
> 

Sure, will add this info to the commit message.

The __string accessors and friends were available when original commit was merged.
Original commit uses such functions for another field.
Thus, I suppose, it is ok to backport all the way to that commit id.

- - 
Thanks,
Sasha