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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, Mina Almasry Subject: Re: [PATCH net v2] net: devmem: prevent net-iov / page mixing Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Jul 27, 2026 at 12:19:37PM +0100, Pavel Begunkov wrote: > We should either have net_iov or page backed frags in a single skb, > otherwise it blows up down the stack. Don't allow mixing in > zerocopy_fill_skb_from_devmem(). > > Fixes: bd61848900bff ("net: devmem: Implement TX path") > Cc: stable@vger.kernel.org > Signed-off-by: Pavel Begunkov > --- > > v2: EEXIST -> EFAULT, as skb_zerocopy_iter_stream() doesn't handle > the former + for consistency. > > net/core/datagram.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/core/datagram.c b/net/core/datagram.c > index c285c6465923..173b5d97bd40 100644 > --- a/net/core/datagram.c > +++ b/net/core/datagram.c > @@ -712,6 +712,9 @@ zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from, > size_t virt_addr, size, off; > struct net_iov *niov; > > + if (i && skb_frags_readable(skb)) > + return -EFAULT; > + Doesn't this still break the allowed scenario where the user does sendmsg(not devmem) before sendmsg(devmem), and tcp tries to append to the write tail skb? Best, Bobby