Bug 2425127 (CVE-2022-50764)

Summary: CVE-2022-50764 kernel: ipv6/sit: use DEV_STATS_INC() to avoid data-races
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was discovered in the Linux kernel’s IPv6 SIT tunnel implementation, where multiple CPUs may concurrently update the dev->stats.tx_error field without appropriate synchronization. This is caused by the SIT tunnel’s transmit function (ndo_start_xmit()) not being protected by a spinlock due to the NETIF_F_LLTX flag, allowing data races on statistics updates, leading to inconsistent statistics and potentially unpredictable kernel behavior
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Description OSIDB Bzimport 2025-12-24 14:04:55 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ipv6/sit: use DEV_STATS_INC() to avoid data-races

syzbot/KCSAN reported that multiple cpus are updating dev->stats.tx_error
concurrently.

This is because sit tunnels are NETIF_F_LLTX, meaning their ndo_start_xmit()
is not protected by a spinlock.

While original KCSAN report was about tx path, rx path has the same issue.
Comment 1 Alexander B 2025-12-25 00:28:36 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122456-CVE-2022-50764-45eb@gregkh/T