CVE-2026-99192: net: bcmgenet: unshare the skb before writing the control block

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

net: bcmgenet: unshare the skb before writing the control block

bcmgenet stores firstcb, lastcb and bytessent in the skb control block and reads them back on completion to free the skb and credit BQL. ethersetup() leaves IFFTXSKBSHARING set, so the stack can resubmit a shared skb that is still in the ring. The next transmit overwrites lastcb, so the earlier slots complete without crediting their bytes and BQL stalls the queue until the watchdog resets it.

Unshare the skb before writing the control block.

Reproduce with pktgen in cloneskb mode, which hands the driver the same skb while earlier copies are still in the ring:

modprobe pktgen pg=/proc/net/pktgen echo "adddevice eth0" > $pg/kpktgend0 echo "dstmac AA:BB:CC:DD:EE:FF" > $pg/eth0 echo "dst 192.0.2.1" > $pg/eth0 echo "cloneskb 8" > $pg/eth0 echo "count 0" > $pg/eth0 echo start > $pg/pgctrl & sleep 5 echo stop > $pg/pgctrl wait cat /sys/class/net/eth0/queues/tx-0/bytequeuelimits/inflight

inflight stays nonzero on the now idle queue. cloneskb 0 leaves it at zero.