Re: [PATCH 120/190] Revert "tty: atmel_serial: fix a potential NULL pointer dereference"

[Richard Genoud]

Le 22/04/2021 à 07:18, Jiri Slaby a écrit :
> On 21. 04. 21, 14:59, Greg Kroah-Hartman wrote:
> > This reverts commit c85be041065c0be8bc48eda4c45e0319caf1d0e5.
> >
> > Commits from @umn.edu addresses have been found to be submitted in "bad
> > faith" to try to test the kernel community's ability to review "known
> > malicious" changes.  The result of these submissions can be found in a
> > paper published at the 42nd IEEE Symposium on Security and Privacy
> > entitled, "Open Source Insecurity: Stealthily Introducing
> > Vulnerabilities via Hypocrite Commits" written by Qiushi Wu (University
> > of Minnesota) and Kangjie Lu (University of Minnesota).
> >
> > Because of this, all submissions from this group must be reverted from
> > the kernel tree and will need to be re-reviewed again to determine if
> > they actually are a valid fix.  Until that work is complete, remove this
> > change to ensure that no problems are being introduced into the
> > codebase.
> >
> > Cc: Kangjie Lu <kjlu@xxxxxxx>
> > Cc: Richard Genoud <richard.genoud@xxxxxxxxx>
> > Cc: stable <stable@xxxxxxxxxxxxxxx>
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/tty/serial/atmel_serial.c | 4 ----
> >   1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> > index a24e5c2b30bc..9786d8e5f04f 100644
> > --- a/drivers/tty/serial/atmel_serial.c
> > +++ b/drivers/tty/serial/atmel_serial.c
> > @@ -1256,10 +1256,6 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
> >                        sg_dma_len(&atmel_port->sg_rx)/2,
> >                        DMA_DEV_TO_MEM,
> >                        DMA_PREP_INTERRUPT);
> > -    if (!desc) {
> > -        dev_err(port->dev, "Preparing DMA cyclic failed\n");
> > -        goto chan_err;
> > -    }
>
> I cannot find anything malicious in the original fix:
> * port->dev is valid for dev_err
> * dmaengine_prep_dma_cyclic returns NULL in case of error
> * chan_err invokes atmel_release_rx_dma which undoes the previous initialization code.
>
> Hence a NACK from me for the revert.

I agree with your NACK.
Back at the time (march 2019), I reviewed the changed and asked for a 2nd version and
I didn't found anything suspicious.
But the more eyes, the better.

cf http://lkml.iu.edu/hypermail/linux/kernel/1903.1/05858.html

> >       desc->callback = atmel_complete_rx_dma;
> >       desc->callback_param = port;
> >       atmel_port->desc_rx = desc;