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([2001:ee0:4f0e:fb30:37c0:6356:b7b4:119a]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23c8455d153sm115207925ad.94.2025.07.08.07.58.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jul 2025 07:58:31 -0700 (PDT) Message-ID: Date: Tue, 8 Jul 2025 21:58:24 +0700 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] virtio-net: fix received length check in big packets To: Parav Pandit , "netdev@vger.kernel.org" Cc: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Minggang(Gavin) Li" , Gavi Teitz , "virtualization@lists.linux.dev" , "linux-kernel@vger.kernel.org" References: <20250708144206.95091-1-minhquangbui99@gmail.com> Content-Language: en-US From: Bui Quang Minh In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/8/25 21:52, Parav Pandit wrote: >> From: Bui Quang Minh >> Sent: 08 July 2025 08:12 PM >> >> Since commit 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big >> packets"), the allocated size for big packets is not MAX_SKB_FRAGS * >> PAGE_SIZE anymore but depends on negotiated MTU. The number of >> allocated frags for big packets is stored in >> vi->big_packets_num_skbfrags. This commit fixes the received length >> check corresponding to that change. The current incorrect check can lead to >> NULL page pointer dereference in the below while loop when erroneous >> length is received. > Do you mean a device has copied X bytes in receive buffer but device reports X+Y bytes in the ring? Yes, that's what I mean. AFAIK, it's not checked in the ring level. Thanks, Quang Minh. > >> Fixes: 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big >> packets") >> Signed-off-by: Bui Quang Minh >> --- >> Changes in v2: >> - Remove incorrect give_pages call >> --- >> drivers/net/virtio_net.c | 9 ++++++--- >> 1 file changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index >> 5d674eb9a0f2..3a7f435c95ae 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -823,7 +823,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info >> *vi, { >> struct sk_buff *skb; >> struct virtio_net_common_hdr *hdr; >> - unsigned int copy, hdr_len, hdr_padded_len; >> + unsigned int copy, hdr_len, hdr_padded_len, max_remaining_len; >> struct page *page_to_free = NULL; >> int tailroom, shinfo_size; >> char *p, *hdr_p, *buf; >> @@ -887,12 +887,15 @@ static struct sk_buff *page_to_skb(struct >> virtnet_info *vi, >> * tries to receive more than is possible. This is usually >> * the case of a broken device. >> */ >> - if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) { >> + BUG_ON(offset >= PAGE_SIZE); >> + max_remaining_len = (unsigned int)PAGE_SIZE - offset; >> + max_remaining_len += vi->big_packets_num_skbfrags * PAGE_SIZE; >> + if (unlikely(len > max_remaining_len)) { >> net_dbg_ratelimited("%s: too much data\n", skb->dev- >>> name); >> dev_kfree_skb(skb); >> return NULL; >> } >> - BUG_ON(offset >= PAGE_SIZE); >> + >> while (len) { >> unsigned int frag_size = min((unsigned)PAGE_SIZE - offset, >> len); >> skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset, >> -- >> 2.43.0