Messages in this thread | | | Date | Sun, 23 Jul 2023 17:33:54 +0800 (GMT+08:00) | From | "Lin Ma" <> | Subject | Re: [PATCH v1] vdpa: Complement vdpa_nl_policy for nlattr length check |
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Hello Michael,
> > > > The vdpa_nl_policy structure is used to validate the nlattr when parsing > > the incoming nlmsg. It will ensure the attribute being described produces > > a valid nlattr pointer in info->attrs before entering into each handler > > in vdpa_nl_ops. > > > > That is to say, the missing part in vdpa_nl_policy may lead to illegal > > nlattr after parsing, which could lead to OOB read just like CVE-2023-3773. > > Hmm. > > https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-3773 > > ** RESERVED ** This candidate has been reserved by an organization or individual that will use it when announcing a new security problem. When the candidate has been publicized, the details for this candidate will be provided. >
Yeah, that CVE is assigned while fix not upstream yet. FYI, the fix is pending too. See, https://marc.info/?l=linux-kernel&m=169009801131058&w=2.
> > > This patch adds three missing nla_policy to avoid such bugs. > > > > Fixes: 90fea5a800c3 ("vdpa: device feature provisioning") > > Fixes: 13b00b135665 ("vdpa: Add support for querying vendor statistics") > > Fixes: ad69dd0bf26b ("vdpa: Introduce query of device config layout") > > Signed-off-by: Lin Ma <linma@zju.edu.cn> > > I don't know how OOB triggers but this duplication is problematic I > think: we are likely to forget again in the future. Isn't there a way > to block everything that is not listed? >
Sure, that is another undergoing task I'm working on. If the nlattr is parsed with NL_VALIDATE_UNSPEC, any forgotten nlattr will be rejected, therefore (which is the default for modern nla_parse). The problem here is that there are still consumers for nla_parse_deprecated. And we cannot simply replace all *_deprecated to modern ones as it may break userspace. See the commit message in 8cb081746c03 ("netlink: make validation more configurable for future strictness")
I believe if we can do enough test against userspace toolchains, we can ultimately upgrade all *_depprecated parsers to modern ones, which costs time and efforts. This send patch is a much simpler (but temporary) solution for now.
Regards Lin
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