Re: [PATCH] Input: ims-pcu - bound frame parser write index against read_buf size

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Fri, Apr 24, 2026 at 06:16:57AM +0200, Greg Kroah-Hartman wrote:
> On Thu, Apr 23, 2026 at 10:24:08AM -0700, Dmitry Torokhov wrote:
> > On Thu, Apr 23, 2026 at 06:52:23AM +0200, Greg Kroah-Hartman wrote:
> > > On Wed, Apr 22, 2026 at 06:36:24PM -0700, Dmitry Torokhov wrote:
> > > > Hi Greg,
> > > > 
> > > > On Mon, Apr 20, 2026 at 09:05:31PM +0200, Greg Kroah-Hartman wrote:
> > > > > ims_pcu_process_data() implements a STX/DLE/ETX byte-stuffing parser
> > > > > that accumulates frame payload into pcu->read_buf[] using the running
> > > > > index pcu->read_pos.  read_buf is IMS_PCU_BUF_SIZE (128) bytes and
> > > > > read_pos is u8 but of course, we don't check the index before actually
> > > > > writing the data :(
> > > > > 
> > > > > Fix this up by properly rejecting the frame at the first attempt to
> > > > > write past read_buf and resync on the next STX, mirroring how the parser
> > > > > handles short and bad-checksum frames on ETX.
> > > > > 
> > > > > Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > > > > Fixes: 628329d52474 ("Input: add IMS Passenger Control Unit driver")
> > > > > Cc: stable <stable@kernel.org>
> > > > > Assisted-by: gkh_clanker_t1000
> > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > > 
> > > > I already have a patch for this, thanks.
> > > 
> > > Ah, missed that, sorry, I was working against Linus's tree.  I am
> > > guessing you are referring to commit 875115b82c29 ("Input: ims-pcu - fix
> > > heap-buffer-overflow in ims_pcu_process_data()")?  If so, why wasn't
> > > that tagged for stable inclusion?
> > 
> > I do not believe it is worth it. The driver is for specialized hardware,
> > so common distros will not be enabling it, and systems where it is used
> > likely do not allow plugging weird stuff into them and probably do not
> > use stable either.
> 
> Android allows a lot of odd things to be plugged into it :(

Well, that's on them. Do they enable drivers blindly?

> 
> > I actually wonder if we need to carry the driver or if we should simply
> > drop it. The only non-cleanup change to it was done in 2014.
> 
> I'll gladly send a patch to delete it if you want me to.

Sure, let's do it. It's easy to restore it if it is actually needed.

Thanks.

-- 
Dmitry