Date: Tue, 20 Mar 2012 18:02:49 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Serge Hallyn <serge.hallyn@...onical.com> cc: Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org, Darren Hart <dvhart@...ux.intel.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Andrew Morton <akpm@...ux-foundation.org>, Jiri Kosina <jkosina@...e.cz>, "Eric W. Biederman" <ebiederm@...ssion.com>, David Howells <dhowells@...hat.com>, kernel-hardening@...ts.openwall.com, spender@...ecurity.net, mingo@...nel.org Subject: Re: [PATCH] futex: do not leak robust list to unprivileged process On Tue, 20 Mar 2012, Serge Hallyn wrote: > Quoting Kees Cook (keescook@...omium.org): > > It was possible to extract the robust list head address from a setuid > > process if it had used set_robust_list(), allowing an ASLR info leak. This > > changes the permission checks to be the same as those used for similar > > info that comes out of /proc. > > > > Running a setuid program that uses robust futexes would have had: > > cred->euid != pcred->euid > > cred->euid == pcred->uid > > so the old permissions check would allow it. I'm not aware of any setuid > > programs that use robust futexes, so this is just a preventative measure. > > > > (This patch is based on changes from grsecurity.) > > > > Signed-off-by: Kees Cook <keescook@...omium.org> > > I like the change. Much cleaner. I'm not 100% sure though that > there are no legitimate cases of robust futexes use which would now > be forbidden. (Explicitly cc:ing Ingo) get_robust_list is not necessary for robust futexes. There is no reference to get_robust_list in glibc. I really wonder why we have this syscall at all. Thanks, tglx
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