From: Florian Weimer <fweimer@redhat.com>
To: Topi Miettinen <toiwoton@gmail.com>
Cc: 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>,
Lennart Poettering <mzxreary@0pointer.de>,
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 10:25:22 +0200 [thread overview]
Message-ID: <87d01asm4t.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <511318fd-efde-f2fc-9159-9d16ac8d33a7@gmail.com> (Topi Miettinen's message of "Thu, 22 Oct 2020 11:17:19 +0300")
* Topi Miettinen:
>> 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?
Is that architecturally supported? How costly is the mprotect change if
the pages have not been faulted in yet?
> 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?
Eventually, I expect that mainstream distributions build everything for
BTI, so yes, the PROT_BTI removal would only be needed for legacy
programs.
Thanks,
Florian
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next prev parent reply other threads:[~2020-10-22 8:27 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 [this message]
2020-10-22 8:29 ` Szabolcs Nagy
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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