CVE-2025-40292

In the Linux kernel, the following vulnerability has been resolved:

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.