Date: Tue, 8 May 2012 04:31:53 +0400 From: Solar Designer <solar@...nwall.com> To: oss-security@...ts.openwall.com Subject: Re: CVE Request -- kernel: futex: clear robust_list on execve Petr, all - On Tue, May 08, 2012 at 04:08:17AM +0400, Solar Designer wrote: > Indeed, execve() may make the new process relatively privileged (SUID, > SGID, fscaps), and thus being able to write into its memory is a > security issue. However, it appears that robust_list (and its compat > counterpart) is only used for such writes when the process itself is > exiting (with the aim being to notify other threads sharing the same > mm). If so, the question is whether and how writes into an exiting > process' memory may be exploited. We're already in do_exit() at this > point, and it's just a few lines before we detach from and likely > destroy the mm. Well, if that process itself is multi-threaded (and > other threads are not exiting yet), it possibly can be exploited > (through affecting those other threads). https://bugzilla.redhat.com/show_bug.cgi?id=771764#c4 describes that the bug was inadvertently triggered in normal usage of certain programs, and how it was rather difficult to figure out. My question is: was exit of a multi-threaded program involved and relevant? If not, then there must be something wrong with my reasoning, because I don't currently see how the bug may otherwise have visible consequences. Alexander
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