Date: Tue, 9 Aug 2022 23:22:32 +0200 From: Vegard Nossum <vegard.nossum@...cle.com> To: oss-security@...ts.openwall.com Subject: Re: CVE-2022-2588 - Linux kernel cls_route UAF On 8/9/22 19:11, Thadeu Lima de Souza Cascardo wrote: > CVE-2022-2588 - Linux kernel cls_route UAF > > It was discovered that the cls_route filter implementation in the Linux kernel > would not remove an old filter from the hashtable before freeing it if its > handle had the value 0. > > Zhenpeng Lin working with Trend Micro's Zero Day Initiative discovered that > this vulnerability could be exploited for Local Privilege Escalation. This has > been reported as ZDI-CAN-17440, and assigned CVE-2022-2588. > > This bug has been present since the first Linux commit git, v2.6.12-rc2. > > Exploiting it requires CAP_NET_ADMIN in any user or network namespace. > > It can be mitigated by those users who do not rely on cls_route, by adding > 'install cls_route /bin/true' to their modprobe.conf or modprobe.d configs, > in case it's built as a module. > > A PoC that will trigger a WARNING is going to be posted in a week. > > Fixes have been sent to netdev@...r.kernel.org and are at > https://firstname.lastname@example.org/T/#u. This isn't the first bug where users can use namespaces to load kernel modules they wouldn't otherwise be able to load, thus increasing attack surface. I've posted a patch that attempts to mitigate this somewhat here (it would have prevented the above bug from being exploited for what is most likely a majority of users): https://email@example.com/ There is apparently also a parallel discussion about user namespaces and LSM hooks here that seems relevant: https://lwn.net/Articles/903580/ Vegard
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