Messages in this thread | | | From | Eric Dumazet <> | Date | Thu, 12 May 2022 11:13:46 -0700 | Subject | Re: BUG: TCP timewait sockets survive across namespace creation in net-next |
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On Thu, May 12, 2022 at 11:01 AM Leonard Crestez <cdleonard@gmail.com> wrote: > > Hello, > > It appears that in recent net-next versions it is possible for sockets > in the timewait state to survive across namespace add/del. Timewait > sockets are inserted into a global hash and only the sock_net value is > compared when they are enumerated from interfaces like /proc/net/tcp and > inet_diag. Old TW sockets are not cleared after namespace delete and > namespaces are allocated from a slab and thus their pointers get reused > a lot, when that happens timewait sockets from an old namespace will > show up in the new one. > > This can be reproduced by establishing a TCP connection over a veth pair > between two namespaces, closing and then recreating those namespaces. > Old timewait sockets will be visible and it happens quite reliably, > often on the first iteration. I can try to provide a script for this. > > I can't point to specific bugs outside of tests that explicitly > enumerate timewait sockets but letting sk_net be a dangling pointer > seems very dangerous. It also violates the idea of network namespaces > being independent and isolated. > > This does not happen in 5.17, I bisected this behavior to commit > 0dad4087a86a ("tcp/dccp: get rid of inet_twsk_purge()") >
Thanks for the report.
I guess we will need to store the (struct net)->net_cookie to disambiguate the case where a new 'struct net' is reusing the same storage than an old one.
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