Linux Kernel bcmgenet Driver: skb Sharing Leads to BQL Stall
CVE-2026-99192 Published on October 28, 2026
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 first_cb, last_cb and bytes_sent in the skb control
block and reads them back on completion to free the skb and credit BQL.
ether_setup() leaves IFF_TX_SKB_SHARING set, so the stack can resubmit
a shared skb that is still in the ring. The next transmit overwrites
last_cb, 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 clone_skb mode, which hands the driver the same
skb while earlier copies are still in the ring:
modprobe pktgen
pg=/proc/net/pktgen
echo "add_device eth0" > $pg/kpktgend_0
echo "dst_mac AA:BB:CC:DD:EE:FF" > $pg/eth0
echo "dst 192.0.2.1" > $pg/eth0
echo "clone_skb 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/byte_queue_limits/inflight
inflight stays nonzero on the now idle queue. clone_skb 0 leaves it at
zero.
Products Associated with CVE-2026-99192
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Affected Versions
Linux:- Version f48bed16a756f5bc0244acd581f61968f7d7c2a4 and below 40c04abcbc34e3afe338f41dae851ecbd72852ac is affected.
- Version f48bed16a756f5bc0244acd581f61968f7d7c2a4 and below 7939ad3b4db9eadf45a64f0524f38337a9494672 is affected.
- Version f48bed16a756f5bc0244acd581f61968f7d7c2a4 and below 89771ce4f8f67dcffae561b2ccac95c0f6e3aa01 is affected.
- Version fb4ca2b4bc6712a6ad635df5b9b41131846589f9 is affected.
- Version 3.16.50 and below 3.17 is affected.
- Version 4.13 is affected.
- Before 4.13 is unaffected.
- Version 6.18.59, <= 6.18.* is unaffected.
- Version 7.2.13, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.