| Message ID | 20180727084447.13984-1-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | dmaengine: rcar-dmac: Make rcar_dmac_of_xlate() more robust | expand |
Hi Geert, Thank you for the patch. On Friday, 27 July 2018 11:44:47 EEST Geert Uytterhoeven wrote: > Add an upper bound check for the MID/RID value passed from DT via the > DMA spec. > > This avoids writing to reserved bits in the DMARS registers in case of > an out-of-range value in DT. Is this really useful ? In the normal case, when information in DT is correct, this will just add overhead. What do we really want to guard against ? If we merge this change, how much further do we need to go ? What other values provided in DT, such as reg addresses, do we need to validate them too ? Functionally speaking this change does no harm, but it increases the kernel size, add overhead at runtime, and only addresses a very limited range of invalid DT issues. > Suggested-by: Renesas BSP team via Yoshihiro Shimoda > <yoshihiro.shimoda.uh@renesas.com> Signed-off-by: Geert Uytterhoeven > <geert+renesas@glider.be> > --- > drivers/dma/sh/rcar-dmac.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c > index 72572320208dbb9a..73cf1053bed90244 100644 > --- a/drivers/dma/sh/rcar-dmac.c > +++ b/drivers/dma/sh/rcar-dmac.c > @@ -1644,8 +1644,11 @@ static struct dma_chan *rcar_dmac_of_xlate(struct > of_phandle_args *dma_spec, struct dma_chan *chan; > dma_cap_mask_t mask; > > - if (dma_spec->args_count != 1) > + if (dma_spec->args_count != 1 || dma_spec->args[0] > 0xff) { > + pr_info("%s: invalid MID/RID 0x%x... for %pOF\n", __func__, > + dma_spec->args[0], dma_spec->np); > return NULL; > + } > > /* Only slave DMA channels can be allocated via DT */ > dma_cap_zero(mask);
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index 72572320208dbb9a..73cf1053bed90244 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -1644,8 +1644,11 @@ static struct dma_chan *rcar_dmac_of_xlate(struct of_phandle_args *dma_spec, struct dma_chan *chan; dma_cap_mask_t mask; - if (dma_spec->args_count != 1) + if (dma_spec->args_count != 1 || dma_spec->args[0] > 0xff) { + pr_info("%s: invalid MID/RID 0x%x... for %pOF\n", __func__, + dma_spec->args[0], dma_spec->np); return NULL; + } /* Only slave DMA channels can be allocated via DT */ dma_cap_zero(mask);
Add an upper bound check for the MID/RID value passed from DT via the DMA spec. This avoids writing to reserved bits in the DMARS registers in case of an out-of-range value in DT. Suggested-by: Renesas BSP team via Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- drivers/dma/sh/rcar-dmac.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)