Re: [PATCH] net: stmmac: guard FCS stripping against runt frames

[Lorenzo Bianconi]

> On Thu, Sep 24, 2026 at 09:57:14AM +0200, Lorenzo Bianconi wrote:
> > > > > @@ -5808,10 +5809,10 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
> > > > >  
> > > > >  		/* ACS is disabled; strip manually. */
> > > > >  		if (likely(!(status & rx_not_ls))) {
> > > > > -			if (buf2_len) {
> > > > > +			if (buf2_len >= ETH_FCS_LEN) {
> > > > 
> > > > I do not think this approach is correct since, at least theoretically, the FCS can be
> > > > splitted between buf1 and buf2.
> > > 
> > > We are talking about runt frames here, so less than 64 bytes in
> > > size. Can such a frame be split over two buffers? What is the minimum
> > > size of the first buffer?
> > 
> > Why are talking just about runt frames?  According to my understanding,
> > this codebase (at least the one in stmmac_rx()) is executed on all
> > 'last fragments'. Am I missing something?
> 
> That the patch subject is wrong?
> 
> [PATCH] net: stmmac: guard FCS stripping against runt frames

ack, I missed the subject, but I think it is wrong, the issue is not just on
runt frames.

Regards,
Lorenzo

> 
> I suspect this is an AI generated bug report, a minimal fix has been
> proposed, but no actual thought applied to the situation, such as does
> the hardware even allow it to happen, does it apply to more complex
> situations, such as fragmentation etc. The usual AI problems....
> 
> 	Andrew

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