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From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Topi Miettinen <toiwoton@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>,
	Lennart Poettering <mzxreary@0pointer.de>,
	Mark Rutland <mark.rutland@arm.com>,
	systemd-devel@lists.freedesktop.org,
	Kees Cook <keescook@chromium.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Mark Brown <broonie@kernel.org>,
	libc-alpha@sourceware.org, Dave Martin <dave.martin@arm.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [systemd-devel] BTI interaction between seccomp filters in systemd and glibc mprotect calls, causing service failures
Date: Thu, 22 Oct 2020 09:29:12 +0100	[thread overview]
Message-ID: <20201022082912.GQ3819@arm.com> (raw)
In-Reply-To: <511318fd-efde-f2fc-9159-9d16ac8d33a7@gmail.com>

The 10/22/2020 11:17, Topi Miettinen via Libc-alpha wrote:
> On 22.10.2020 10.54, Florian Weimer wrote:
> > * Lennart Poettering:
> > > Did you see Topi's comments on the systemd issue?
> > > 
> > > https://github.com/systemd/systemd/issues/17368#issuecomment-710485532
> > > 
> > > I think I agree with this: it's a bit weird to alter the bits after
> > > the fact. Can't glibc set up everything right from the begining? That
> > > would keep both concepts working.
> > 
> > The dynamic loader has to process the LOAD segments to get to the ELF
> > note that says to enable BTI.  Maybe we could do a first pass and load
> > only the segments that cover notes.  But that requires lots of changes
> > to generic code in the loader.
> 
> What if the loader always enabled BTI for PROT_EXEC pages, but then when
> discovering that this was a mistake, mprotect() the pages without BTI? Then
> both BTI and MDWX would work and the penalty of not getting MDWX would fall
> to non-BTI programs. What's the expected proportion of BTI enabled code vs.
> disabled in the future, is it perhaps expected that a distro would enable
> the flag globally so eventually only a few legacy programs might be
> unprotected?

i thought mprotect(PROT_EXEC) would get filtered
with or without bti, is that not the case?

then i guess we can do the protection that way
around, but then i don't see why the filter cannot
treat PROT_EXEC|PROT_BTI the same as PROT_EXEC.


  parent reply	other threads:[~2020-10-22  8:29 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <8584c14f-5c28-9d70-c054-7c78127d84ea@arm.com>
2020-10-22  7:18 ` [systemd-devel] BTI interaction between seccomp filters in systemd and glibc mprotect calls, causing service failures Lennart Poettering
2020-10-22  7:54   ` Florian Weimer
2020-10-22  8:17     ` Topi Miettinen
2020-10-22  8:25       ` Florian Weimer
2020-10-22  8:29       ` Szabolcs Nagy [this message]
2020-10-22  8:38         ` Lennart Poettering
2020-10-22  9:31           ` Catalin Marinas
2020-10-22 10:12             ` Topi Miettinen
2020-10-22 10:27               ` Florian Weimer
2020-10-23  6:13             ` Szabolcs Nagy
2020-10-23  9:04               ` Catalin Marinas
2020-10-22 10:03         ` Topi Miettinen
2020-10-22  8:05   ` Szabolcs Nagy
2020-10-22  8:31     ` Lennart Poettering
     [not found] ` <20201022075447.GO3819@arm.com>
2020-10-22 10:39   ` Topi Miettinen
2020-10-22 20:02     ` Kees Cook
2020-10-22 22:24       ` Topi Miettinen
2020-10-23 17:52         ` Salvatore Mesoraca
2020-10-24 11:34           ` Topi Miettinen
2020-10-24 14:12             ` Salvatore Mesoraca
2020-10-25 13:42               ` Jordan Glover
2020-10-23  9:02       ` Catalin Marinas
2020-10-24 11:01         ` Topi Miettinen
2020-10-26 14:52           ` Catalin Marinas
2020-10-26 15:56             ` Dave Martin
2020-10-26 16:51               ` Mark Brown
2020-10-26 16:31             ` Topi Miettinen
2020-10-26 16:24 ` Dave Martin
2020-10-26 16:39   ` Topi Miettinen
2020-10-26 16:45   ` Florian Weimer
2020-10-27 14:22     ` Dave Martin
2020-10-27 14:41       ` Florian Weimer
2020-10-26 16:57   ` Szabolcs Nagy
2020-10-26 17:52     ` Dave Martin
2020-10-26 22:39       ` Jeremy Linton
2020-10-27 14:15         ` Dave Martin
2020-10-29 11:02           ` Catalin Marinas
2020-11-04 12:18             ` Dave Martin

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