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 MAXSKBFRAGS * PAGESIZE anymore but depends on negotiated MTU. The number of allocated frags for big packets is stored in vi->bigpacketsnumskbfrags.

Because the host announced buffer length can be malicious (e.g. the host vhostnet driver's getrxbufs is modified to announce incorrect length), we need a check in virtionet 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.