lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 29 Oct 2021 17:53:03 -0600 From: David Ahern <dsahern@...il.com> To: msizanoen <msizanoen@...labs.xyz>, davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org, kuba@...nel.org Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: Kernel leaks memory in ip6_dst_cache when suppress_prefix is present in ipv6 routing rules and a `fib` rule is present in ipv6 nftables rules On 10/26/21 8:24 AM, msizanoen wrote: > The kernel leaks memory when a `fib` rule is present in ipv6 nftables > firewall rules and a suppress_prefix rule > is present in the IPv6 routing rules (used by certain tools such as > wg-quick). In such scenarios, every incoming > packet will leak an allocation in ip6_dst_cache slab cache. > > After some hours of `bpftrace`-ing and source code reading, I tracked > down the issue to this commit: > https://github.com/torvalds/linux/commit/ca7a03c4175366a92cee0ccc4fec0038c3266e26 > > > The problem with that patch is that the generic args->flags always have > FIB_LOOKUP_NOREF set[1][2] but the > ip6-specific flag RT6_LOOKUP_F_DST_NOREF might not be specified, leading > to fib6_rule_suppress not > decreasing the refcount when needed. This can be fixed by exposing the > protocol-specific flags to the > protocol specific `suppress` function, and check the protocol-specific > `flags` argument for > RT6_LOOKUP_F_DST_NOREF instead of the generic FIB_LOOKUP_NOREF when > decreasing the refcount. > > How to reproduce: > - Add the following nftables rule to a prerouting chain: `meta nfproto > ipv6 fib saddr . mark . iif oif missing drop` exact command? I have not played with nftables. Do you have a stack trace of where the dst reference is getting taken? > - Run `sudo ip -6 rule add table main suppress_prefixlength 0` > - Watch `sudo slabtop -o | grep ip6_dst_cache` memory usage increase > with every incoming ipv6 packet > > Example > patch:https://gist.github.com/msizanoen1/36a2853467a9bd34fadc5bb3783fde0f > > [1]:https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71 > > [2]:https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99 > > >
Powered by blists - more mailing lists