Messages in this thread | | | From | <> | Subject | Re: [PATCH net] net: macb: fix a memory corruption in extended buffer descriptor mode | Date | Wed, 12 Apr 2023 15:47:30 +0000 |
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Jakub, Roman,
On 12/04/2023 at 06:13, Jakub Kicinski wrote: > On Tue, 11 Apr 2023 20:48:50 -0700 Roman Gushchin wrote: >>> diff --git a/drivers/net/ethernet/cadence/macb_main.c >>> b/drivers/net/ethernet/cadence/macb_main.c >>> index d13fb1d31821..1a40d5a26f36 100644 >>> --- a/drivers/net/ethernet/cadence/macb_main.c >>> +++ b/drivers/net/ethernet/cadence/macb_main.c >>> @@ -1042,6 +1042,10 @@ static dma_addr_t macb_get_addr(struct macb *bp, >>> struct macb_dma_desc *desc) >>> } >>> #endif >>> addr |= MACB_BF(RX_WADDR, MACB_BFEXT(RX_WADDR, desc->addr)); >>> +#ifdef CONFIG_MACB_USE_HWSTAMP >>> + if (bp->hw_dma_cap & HW_DMA_CAP_PTP) >>> + addr &= ~GEM_BIT(DMA_RXVALID_OFFSET); >>> +#endif >>> return addr; >>> } >> >> I think this version is slightly worse because it adds an unconditional >> if statement, which can be removed with certain config options. >> I can master a version with a helper function, if it's preferable. >> >> But if you like this one, it's fine too, let me know, I'll send an updated >> version. > > Yup, IMHO this looks better. More likely that someone reading the code > will spot the trickiness.
Ok with this version, even if adding to the hot path is really a big concern for our low-end CPUs (ARM9 and Cortex-A5).
> I suspect we could clear that bit unconditionally, if the branch is > a concern. The code seems to assume that buffers it gets are 8B aligned > already, regardless of CONFIG_MACB_USE_HWSTAMP. > > Drivers commonly save the DMA address to a SW ring (here I think > rx_skbuff plays this role but only holds single ptr per entry) > so that they don't have to access potentially uncached descriptor > ring. But that'd be too large of a change for a fix.
Ok with that statement:
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Thanks, best regards, Nicolas
-- Nicolas Ferre
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