Bug 2401527 (CVE-2022-50476)

Summary:	CVE-2022-50476 kernel: ntb_netdev: Use dev_kfree_skb_any() in interrupt context
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	---
Doc Text:	An incorrect function call was found in the Linux kernel Non-Transparent Bridge network driver's interrupt handling. When using AMD PTDMA DMA engines, the TX/RX callback handlers are invoked in hard interrupt context but call the interrupt-unsafe dev_kfree_skb() function to free network buffers, which results in kernel warnings and severe TCP/IP performance degradation.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-10-04 16:05:42 UTC

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

ntb_netdev: Use dev_kfree_skb_any() in interrupt context

TX/RX callback handlers (ntb_netdev_tx_handler(),
ntb_netdev_rx_handler()) can be called in interrupt
context via the DMA framework when the respective
DMA operations have completed. As such, any calls
by these routines to free skb's, should use the
interrupt context safe dev_kfree_skb_any() function.

Previously, these callback handlers would call the
interrupt unsafe version of dev_kfree_skb(). This has
not presented an issue on Intel IOAT DMA engines as
that driver utilizes tasklets rather than a hard
interrupt handler, like the AMD PTDMA DMA driver.
On AMD systems, a kernel WARNING message is
encountered, which is being issued from
skb_release_head_state() due to in_hardirq()
being true.

Besides the user visible WARNING from the kernel,
the other symptom of this bug was that TCP/IP performance
across the ntb_netdev interface was very poor, i.e.
approximately an order of magnitude below what was
expected. With the repair to use dev_kfree_skb_any(),
kernel WARNINGs from skb_release_head_state() ceased
and TCP/IP performance, as measured by iperf, was on
par with expected results, approximately 20 Gb/s on
AMD Milan based server. Note that this performance
is comparable with Intel based servers.

Comment 1 Alexander B 2025-10-06 13:45:58 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100438-CVE-2022-50476-f1b3@gregkh/T