Subject: Re: [PATCH net v2] rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present

From: Hyunwoo Kim <[email-masked]>
Date: Fri, 8 May 2026 17:05:06 +0900

On Fri, May 08, 2026 at 03:58:34PM +0800, Jiayuan Chen wrote:
> 
> On 5/8/26 2:42 PM, Hyunwoo Kim wrote:
> > The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE
> > handler in rxrpc_verify_response() copy the skb to a linear one before
> > calling into the security ops only when skb_cloned() is true.  An skb
> > that is not cloned but still carries paged fragments (skb->data_len != 0)
> > falls through to the in-place decryption path, which binds the frag
> > pages directly into the AEAD/skcipher SGL via skb_to_sgvec().
> > 
> > Extend the gate so that any skb with non-linear data is also copied,
> > ensuring the security handler always operates on a fully linear skb.
> > The OOM/trace handling already in place is reused.
> > 
> > Fixes: d0d5c0cd1e71 ("rxrpc: Use skb_unshare() rather than skb_cow_data()")
> > Cc: [email-masked]
> > Signed-off-by: Hyunwoo Kim <[email-masked]>
> > ---
> > Changes in v2:
> > - Use skb_is_nonlinear() instead of skb->data_len
> > - v1: https://lore.kernel.org/all/afKV2zGR6rrelPC7@v4bel/
> > ---
> >   net/rxrpc/call_event.c | 2 +-
> >   net/rxrpc/conn_event.c | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
> > index fdd683261226..a6ad5ff6ec5f 100644
> > --- a/net/rxrpc/call_event.c
> > +++ b/net/rxrpc/call_event.c
> > @@ -334,7 +334,7 @@ bool rxrpc_input_call_event(struct rxrpc_call *call)
> >   			if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA &&
> >   			    sp->hdr.securityIndex != 0 &&
> > -			    skb_cloned(skb)) {
> > +			    (skb_cloned(skb) || skb_is_nonlinear(skb))) {
> >   				/* Unshare the packet so that it can be
> >   				 * modified by in-place decryption.
> >   				 */
> > diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
> > index a2130d25aaa9..632cbeff1f5d 100644
> > --- a/net/rxrpc/conn_event.c
> > +++ b/net/rxrpc/conn_event.c
> > @@ -245,7 +245,7 @@ static int rxrpc_verify_response(struct rxrpc_connection *conn,
> >   {
> >   	int ret;
> > -	if (skb_cloned(skb)) {
> > +	if (skb_cloned(skb) || skb_is_nonlinear(skb)) {
> >   		/* Copy the packet if shared so that we can do in-place
> >   		 * decryption.
> >   		 */
> 
> 
> Why not adopt the same gate as the ESP fix:
> 
> 
>     skb_cloned(skb) || skb_has_frag_list(skb) || skb_has_shared_frag(skb)
> 
> 
> so NIC page_pool RX keeps its zero-copy path while still catching the
> splice-loopback vector?

Yeah, that approach preserves the fast path. I'll test and submit v3.

Best regards,
Hyunwoo Kim