linux-kernel - Re: [PATCH v2] ptp: ocp: fix NULL deref in __handle

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Message-ID: <CAMuE1bH9zPA4Bzk7ZictvbWi6v5uTsE_zUVKkTCeuspDT0D7tw@mail.gmail.com>
Date: Tue, 15 Apr 2025 12:22:01 +0300
From: Sagi Maimon <maimon.sagi@...il.com>
To: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Cc: jonathan.lemon@...il.com, vadim.fedorenko@...ux.dev, 
	richardcochran@...il.com, andrew+netdev@...n.ch, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] ptp: ocp: fix NULL deref in __handle_s for irig/dcf

On Tue, Apr 15, 2025 at 10:00 AM Michal Swiatkowski
<michal.swiatkowski@...ux.intel.com> wrote:
>
> On Tue, Apr 15, 2025 at 09:46:38AM +0300, Sagi Maimon wrote:
> > SMA store/get operations via sysfs can call __handle_signal_outputs
> > or __handle_signal_inputs while irig and dcf pointers remain
> > uninitialized. This leads to a NULL pointer dereference in
> > __handle_s. Add NULL checks for irig and dcf to prevent crashes.
> >
> > Fixes: b286f4e87e32 ("serial: core: Move tty and serdev to be children of serial core port device")
> > Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
> > Signed-off-by: Sagi Maimon <maimon.sagi@...il.com>
> > ---
> > Addressed comments from Paolo Abeni:
> >  - https://www.spinics.net/lists/netdev/msg1082406.html
> > Changes since v1:
> >  - Expanded commit message to clarify the NULL dereference scenario.
> > ---
> >  drivers/ptp/ptp_ocp.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
> > index 7945c6be1f7c..4e4a6f465b01 100644
> > --- a/drivers/ptp/ptp_ocp.c
> > +++ b/drivers/ptp/ptp_ocp.c
> > @@ -2434,15 +2434,19 @@ ptp_ocp_dcf_in(struct ptp_ocp *bp, bool enable)
> >  static void
> >  __handle_signal_outputs(struct ptp_ocp *bp, u32 val)
> >  {
> > -     ptp_ocp_irig_out(bp, val & 0x00100010);
> > -     ptp_ocp_dcf_out(bp, val & 0x00200020);
> > +     if (bp->irig_out)
> > +             ptp_ocp_irig_out(bp, val & 0x00100010);
> > +     if (bp->dcf_out)
> > +             ptp_ocp_dcf_out(bp, val & 0x00200020);
> >  }
> >
> >  static void
> >  __handle_signal_inputs(struct ptp_ocp *bp, u32 val)
> >  {
> > -     ptp_ocp_irig_in(bp, val & 0x00100010);
> > -     ptp_ocp_dcf_in(bp, val & 0x00200020);
> > +     if (bp->irig_out)
> Why not irig_in? Can we asssume that "in" isn't NULL if "out" isn't?
>
Ss part of ocp_resource initiation, irig_in and irig_out initiated separately
(one can be initiated and the other not ) so we can't assume that
> > +             ptp_ocp_irig_in(bp, val & 0x00100010);
> > +     if (bp->dcf_out)
> The same here.
>
> > +             ptp_ocp_dcf_in(bp, val & 0x00200020);
>
> Just my opinion, I will move these checks into ptp_ocp_...() functions
> as bp is passed to a function not bp->sth.
>
> >  }
> >
> >  static u32
> > --
> > 2.47.0