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([2620:10d:c092:600::1:4f63]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-496c45b1c76sm4492315e9.6.2026.07.27.09.39.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jul 2026 09:39:18 -0700 (PDT) Message-ID: <9d8eaf93-9d2d-46aa-8f12-ecfde1a906f2@gmail.com> Date: Mon, 27 Jul 2026 17:39:11 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2] net: devmem: prevent net-iov / page mixing To: Bobby Eshleman Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, Mina Almasry References: Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/27/26 17:07, Bobby Eshleman wrote: > 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? Considering that it crashes the kernel, no, it doesn't. -- Pavel Begunkov