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Comment by rphlx | Hacker News Reader

> which probably means it's possible to use a malformed filesystem to get arbitrary code execution in the kernel.

I'll concede that there are some older vulns allowing that, but if you meant for a reasonably up-to-date Linux or Win7+ system: reference needed.

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https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4913, for instance?

Thanks - didn't hear about that one.

Filesystems are basically parsers that were only originally tested against well-formed input. Upstream Linux developers will happily tell you that you shouldn't allow untrusted users to mount filesystems (or trusted users to mount untrusted filesystems…), but unfortunately that's not really an option in the real world.

Well, for the past 4+ years "arbitrary kernel code execution through mounting a malformed FS" has been considered a major security issue, and a lot of effort does go into finding and fixing stuff like that through fuzzing, code audits, static analysis, etc (for both Linux and Windows). I think it is fair to say that this class of vulns is declining in frequency, with the rate of discovery having peaked somewhere within 2008-2012.

Eh. Bugs get fixed as they're found, but I don't see much evidence of it being taken into consideration when adding new code (in Linux, at least - it wouldn't surprise me if Windows were better in this respect)

Yeah, that is right. A bug can only be fixed once it has been found.. the question now is whether the rate of bugs found is greater than the rate of insertion of new bugs (which I guess is proportional to the number of new lines of code). If not the future is going to be terrible.. :D

If the attacker just provides a file system that contains setuid shells or unsecured device files, that's not really a bug and not remotely exploitable. But it's still a vulnerability.

Hopefully filesystems mounted by normal users will have nosuid,nodev enforced (whoever is responsible for this these days, policykit??). Please tell me I'm correct...

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