The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 0c716703965ffc5ef4311b65cb5d84a703784717 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025110954-lunacy-murkiness-7783@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 0c716703965ffc5ef4311b65cb5d84a703784717 Mon Sep 17 00:00:00 2001 From: Bui Quang Minh minhquangbui99@gmail.com Date: Thu, 30 Oct 2025 21:44:38 +0700 Subject: [PATCH] virtio-net: fix received length check in big packets
Since commit 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big packets"), when guest gso is off, 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.
Because the host announced buffer length can be malicious (e.g. the host vhost_net driver's get_rx_bufs is modified to announce incorrect length), we need a check in virtio_net receive path. Currently, the check is not adapted to the new change which can lead to NULL page pointer dereference in the below while loop when receiving length that is larger than the allocated one.
This commit fixes the received length check corresponding to the new change.
Fixes: 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big packets") Cc: stable@vger.kernel.org Signed-off-by: Bui Quang Minh minhquangbui99@gmail.com Reviewed-by: Xuan Zhuo xuanzhuo@linux.alibaba.com Tested-by: Lei Yang leiyang@redhat.com Link: https://patch.msgid.link/20251030144438.7582-1-minhquangbui99@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index e6e650bc3bc3..8855a994e12b 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -910,17 +910,6 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, goto ok; }
- /* - * Verify that we can indeed put this data into a skb. - * This is here to handle cases when the device erroneously - * tries to receive more than is possible. This is usually - * the case of a broken device. - */ - if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) { - 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); @@ -2112,9 +2101,19 @@ static struct sk_buff *receive_big(struct net_device *dev, struct virtnet_rq_stats *stats) { struct page *page = buf; - struct sk_buff *skb = - page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, 0); + struct sk_buff *skb;
+ /* Make sure that len does not exceed the size allocated in + * add_recvbuf_big. + */ + if (unlikely(len > (vi->big_packets_num_skbfrags + 1) * PAGE_SIZE)) { + pr_debug("%s: rx error: len %u exceeds allocated size %lu\n", + dev->name, len, + (vi->big_packets_num_skbfrags + 1) * PAGE_SIZE); + goto err; + } + + skb = page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, 0); u64_stats_add(&stats->bytes, len - vi->hdr_len); if (unlikely(!skb)) goto err;