Messages in this thread | | | Date | Sun, 4 May 2003 09:51:51 -0400 (EDT) | From | Ingo Molnar <> | Subject | Re: [Announcement] "Exec Shield", new Linux security feature |
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On Sun, 4 May 2003, Yoav Weiss wrote:
> I don't see how the case of mprotect(HIGH_ADDRESS, LEN, PROT_EXEC) be > handled. Unlike mremap, mprotect doesn't offer a way to inform the user > about a change of address. > > If I understand correctly, such case will cause a call to > arch_add_exec_range(current->mm, vma) without any remapping, thus > breaking the protection.
yes - the patch does not put any limit on which areas can be PROT_EXEC - if the executable area is 'too wide' then there's no protection. The patch tries to relocate areas which are freely relocatable, to make sure that in the usual case the exec-limit will be quite low.
> One case where this would happen is some of the ancient loaders. IIRC, > libc4's loader did just that. (right, nobody uses it anymore :)
yeah, we should not be worried about old loaders.
> For that reason, maybe X_workaround should be controlled per-executable > by another ELF flag and not as a system-wide property.
i'll remove X_workaround from the next patch altogether - X can be fixed by enabling an executable stack for the binary.
Ingo
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