Messages in this thread | | | Date | Tue, 20 Mar 2012 18:02:49 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] futex: do not leak robust list to unprivileged process |
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On Tue, 20 Mar 2012, Serge Hallyn wrote:
> Quoting Kees Cook (keescook@chromium.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@chromium.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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