This is a robustness hardening patch. The slow-path frag loop in page_to_skb() walks the page chain via page->private until the device-reported len is consumed, implicitly trusting that len fits the chain. It does not stop when the chain is exhausted (page becomes NULL at the tail), nor when nr_frags reaches the end of the static skb_shinfo()->frags[MAX_SKB_FRAGS] array.
Both bounds are needed: the chain length is big_packets_num_skbfrags + 1 pages, which for an MTU-driven configuration can be well below MAX_SKB_FRAGS, so neither guard implies the other. Make the loop self-defending so it no longer relies on the caller having validated len: stop once the chain is exhausted, and never index past MAX_SKB_FRAGS. No functional change for well-formed input. Signed-off-by: Xiang Mei <[email protected]> --- v2: robustness patch drivers/net/virtio_net.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index afe73eda1491..518c22fa1b68 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -906,8 +906,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, } BUG_ON(offset >= PAGE_SIZE); - while (len) { + while (len && page) { unsigned int frag_size = min((unsigned)PAGE_SIZE - offset, len); + + if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) + break; skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset, frag_size, truesize); len -= frag_size; -- 2.43.0
