Hi Geert-san,
> Hi Shimoda-san,
>
> On Fri, Jan 30, 2015 at 7:58 AM, Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > This patch fixes an issue that the following commit causes NULL
> > pointer dereference in dma_release_channel().
> > "usb: renesas_usbhs: add support for requesting DT DMA"
> > (commit id abd2dbf6bb1b5f3a03a8c76b1a8879da1dd30caa)
>
> Thanks for your patch!
>
> > The usbhsf_dma_init_dt() should set fifo->{t,r}x_chan to NULL if
> > dma_request_slave_channel_reason() returns IS_ERR value.
> > Otherwise, usbhsf_dma_quit() will call dma_release_channel(), and then
> > NULL pointer dereference happens.
>
> I guess it also causes other problems?
> The return value of usbhsf_dma_chan_get() is not checked for an error
> code in many callsites.
Yes, you are correct. So, I also should have tested this patch on PIO environment.
> > Reported-by: Simon Horman <horms@xxxxxxxxxxxx>
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
>
> Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Thank you! This patch was already merged in Felipe's repository.
Best regards,
Yoshihiro Shimoda
> > ---
> > This patch is based on Felipe's usb.git / testing/next branch.
> > (commit id =7db3990cb707ff91cd6507d53a0a730afe97)
> >
> > drivers/usb/renesas_usbhs/fifo.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/usb/renesas_usbhs/fifo.c b/drivers/usb/renesas_usbhs/fifo.c
> > index 4c086b1..d891bff 100644
> > --- a/drivers/usb/renesas_usbhs/fifo.c
> > +++ b/drivers/usb/renesas_usbhs/fifo.c
> > @@ -1072,7 +1072,11 @@ static void usbhsf_dma_init_pdev(struct usbhs_fifo *fifo)
> > static void usbhsf_dma_init_dt(struct device *dev, struct usbhs_fifo *fifo)
> > {
> > fifo->tx_chan = dma_request_slave_channel_reason(dev, "tx");
> > + if (IS_ERR(fifo->tx_chan))
> > + fifo->tx_chan = NULL;
> > fifo->rx_chan = dma_request_slave_channel_reason(dev, "rx");
> > + if (IS_ERR(fifo->rx_chan))
> > + fifo->rx_chan = NULL;
> > }
>
> My first thought was: shouldn't it be handled in usbhsf_dma_init() instead,
> so it applies to both the legacy platform data and the DT case?
>
> But apparently dma_request_channel() returns NULL on failure, while
> dma_request_slave_channel_reason() returns an error code. Oh well...
>
> Remapping the error to NULL does mean the driver doesn't handle
> -EPROBE_DEFER, but that's tricky with DMA engines anyway, cfr. commit
> 55f5f9862a31e2ac ("i2c: sh_mobile: rework deferred probing")
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
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