| Message ID | 20210501082822.726-1-jonathon.reinhart@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | net: Only allow init netns to set default tcp cong to a restricted algo | expand |
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Sat, 1 May 2021 04:28:22 -0400 you wrote: > 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 ("net: Make tcp_allowed_congestion_control > readonly in non-init netns") > > [...] Here is the summary with links: - net: Only allow init netns to set default tcp cong to a restricted algo https://git.kernel.org/netdev/net/c/8d432592f30f You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 563d016e7478..db5831e6c136 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -230,6 +230,10 @@ int tcp_set_default_congestion_control(struct net *net, const char *name) ret = -ENOENT; } else if (!bpf_try_module_get(ca, ca->owner)) { ret = -EBUSY; + } else if (!net_eq(net, &init_net) && + !(ca->flags & TCP_CONG_NON_RESTRICTED)) { + /* Only init netns can set default to a restricted algorithm */ + ret = -EPERM; } else { prev = xchg(&net->ipv4.tcp_congestion_control, ca); if (prev)
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 ("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: 6670e1524477 ("tcp: Namespace-ify sysctl_tcp_default_congestion_control") Signed-off-by: Jonathon Reinhart <jonathon.reinhart@gmail.com> --- net/ipv4/tcp_cong.c | 4 ++++ 1 file changed, 4 insertions(+)