Re: [patch] remove MNT_NOEXEC check for PROT_EXEC MAP_PRIVATE mmaps

From: Stas Sergeev
Date: Thu Sep 28 2006 - 00:32:50 EST


Hugh Dickins wrote:
since executables are typically mapped MAP_PRIVATE, I suspect
your patch will simply break mmap's intended MNT_NOEXEC check.
The one with you mean? But its a user-space issue,
I haven't seen anyone claiming the opposite (and you even
explicitly confirmed it is).

I think you need to face up to the fact that "noexec"
doesn't suit your mount, and just leave it at that.
But noone have answered this question:
Which configuration is more secure - the one where all
the user-writable fs are mounted with "noexec" (in old
sense of noexec), or the one without "noexec" at all
because I should no longer use it here and there (actually,

But I do concede that I'm reluctant to present that patch Alan
encouraged, adding a matching MNT_NOEXEC check to mprotect: it
would be consistent, and I do like consistency, but in this case
fear that change in behaviour may cause new userspace breakage.
I can't think of a single real-life example where it will
break something over whatever is broken already by the mmap
check. But I am not encouraging such a change of course.

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