UBUNTU-CVE-2026-98277: Medium severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: eth: fbnic: ring the doorbell if a burst ends in a drop fbnictxmap() skips the doorbell write, and the completion request, for every packet handed to it with xmitmore set, counting on the packet which ends the burst to publish them all. When that packet is dropped instead - skbputpadto(), skbcowhead() or a DMA mapping failure - nothing rings. The descriptors of the preceding packets stay invisible to the HW until the next transmit on that queue, which for a burst-then-idle workload may never come. Remember the meta descriptor of the last packet left without a doorbell and flush it from the error paths. The completion request has to be set on that descriptor rather than simply writing the tail, otherwise the HW would transmit the packets but never report a head, and the ring would fill up and stall for good. This is very similar to Joe's recent series of fixes for bnxt. Not seen in real life, reproduced under QEMU with failure injection.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
What conditions are required to trigger the issue?
The affected fbnic transmit queue must process a burst of packets marked with xmit_more, and the packet that would end and publish that burst must be dropped. The described drop paths include skb_put_padto(), skb_cow_head(), and DMA mapping failures.
What is the operational impact if it occurs?
Descriptors from earlier packets in the burst can remain invisible to the hardware until another transmission occurs on the same queue. In a burst-then-idle workload, that transmission may never occur; if completions are not requested correctly, the ring can eventually fill and stall permanently.
How can I recognize a potentially affected system?
Look for a transmit queue that stops making progress after a packet-drop error at the end of an xmit_more burst, particularly during burst-then-idle traffic patterns. The issue was reproduced with failure injection under QEMU and was not reported as seen in real-world use.