CVE-2021-47010 Information

Description

In the Linux kernel the following vulnerability has been resolved:

net: Only allow init netns to set default tcp cong to a restricted algo

tcp_set_default_congestion_control() is netns-safe in that it writes to &net->ipv4.tcp_congestion_control but it also sets ca->flags |= TCP_CONG_NON_RESTRICTED which is not namespaced. This has the unintended side-effect of changing the global net.ipv4.tcp_allowed_congestion_control sysctl despite the fact that it is read-only: 97684f0970f6 ( et: Make tcp_allowed_congestion_control readonly in non-init netns)

Resolve this netns \leak\ by only allowing the init netns to set the default algorithm to one that is restricted. This restriction could be removed if tcp_allowed_congestion_control were namespace-ified in the future.

This bug was uncovered with https://github.com/JonathonReinhart/linux-netns-sysctl-verify

Reference

https://git.kernel.org/stable/c/992de06308d9a9584d59b96d294ac676f924e437 https://git.kernel.org/stable/c/9884f745108f7d25b189bbcd6754e284fb29ab68 https://git.kernel.org/stable/c/6c1ea8bee75df8fe2184a50fcd0f70bf82986f42 https://git.kernel.org/stable/c/efe1532a6e1a8e3c343d04fff510f0ed80328f9c https://git.kernel.org/stable/c/e7d7bedd507bb732e600403b7a96f9fe48d0ca31 https://git.kernel.org/stable/c/8d432592f30fcc34ef5a10aac4887b4897884493