Re: [PATCH 088/190] Revert "mmc_spi: add a status check for spi_sync_locked"

Ulf Hansson
2021-04-22T08:09:26Z

On Wed, 21 Apr 2021 at 15:19, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Greg,
>
> Thank you for the patch.
>
> On Wed, Apr 21, 2021 at 02:59:23PM +0200, Greg Kroah-Hartman wrote:
> > This reverts commit 611025983b7976df0183390a63a2166411d177f1.
> >
> > 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@umn.edu>
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> I don't spot an obvious issue with the original patch though.
>
> > ---
> > drivers/mmc/host/mmc_spi.c | 4 ----
> > 1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
> > index 02f4fd26e76a..cc40b050e302 100644
> > --- a/drivers/mmc/host/mmc_spi.c
> > +++ b/drivers/mmc/host/mmc_spi.c
> > @@ -800,10 +800,6 @@ mmc_spi_readblock(struct mmc_spi_host *host, struct spi_transfer *t,
> > }
> >
> > status = spi_sync_locked(spi, &host->m);
> > - if (status < 0) {
> > - dev_dbg(&spi->dev, "read error %d\n", status);
> > - return status;
> > - }

Returning here means we never give back the ownership of the buffer to
the CPU. Can that be considered as vulnerability?

If that is that a problem, I can point out that there is already one
more case in this file, where this pattern is repeated. See
mmc_spi_writeblock(). This code has been there since 2007.

> >
> > if (host->dma_dev) {
> > dma_sync_single_for_cpu(host->dma_dev,
>
> --
> Regards,
>
> Laurent Pinchart

Kind regards
Uffe