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Jonathon Reinhart authored
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: 97684f09 ("net: 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



Fixes: 6670e152 ("tcp: Namespace-ify sysctl_tcp_default_congestion_control")
Signed-off-by: default avatarJonathon Reinhart <jonathon.reinhart@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
8d432592
Linux kernel
============

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There are various text files in the Documentation/ subdirectory,
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Please read the Documentation/process/changes.rst file, as it contains the
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