linux-kernel - Re: BTI interaction between seccomp filters in systemd and glibc mprotect calls, causing service failures

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <877drb68ab.fsf@oldenburg2.str.redhat.com>
Date:   Tue, 27 Oct 2020 15:41:16 +0100
From:   Florian Weimer <fweimer@...hat.com>
To:     Dave Martin via Libc-alpha <libc-alpha@...rceware.org>
Cc:     Dave Martin <Dave.Martin@....com>,
        Mark Rutland <mark.rutland@....com>,
        systemd-devel@...ts.freedesktop.org,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Mark Brown <broonie@...nel.org>, toiwoton@...il.com,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: BTI interaction between seccomp filters in systemd and glibc
 mprotect calls, causing service failures

* Dave Martin via Libc-alpha:

> On Mon, Oct 26, 2020 at 05:45:42PM +0100, Florian Weimer via Libc-alpha wrote:
>> * Dave Martin via Libc-alpha:
>> 
>> > Would it now help to add something like:
>> >
>> > int mchangeprot(void *addr, size_t len, int old_flags, int new_flags)
>> > {
>> > 	int ret = -EINVAL;
>> > 	mmap_write_lock(current->mm);
>> > 	if (all vmas in [addr .. addr + len) have
>> > 			their mprotect flags set to old_flags) {
>> >
>> > 		ret = mprotect(addr, len, new_flags);
>> > 	}
>> > 	
>> > 	mmap_write_unlock(current->mm);
>> > 	return ret;
>> > }
>> 
>> I suggested something similar as well.  Ideally, the interface would
>> subsume pkey_mprotect, though, and have a separate flags argument from
>> the protection flags.  But then we run into argument list length limits.
>>
>> Thanks,
>> Florian
>
> I suppose.  Assuming that a syscall filter can inspect memory, we might
> be able to bundle arguments into a struct if necessary.

But that leads to a discussion about batch mmap/mprotect/munmap, and
that's again incompatible with seccomp (it would need a checking loop).

Thanks,
Florian
-- 
Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
Commercial register: Amtsgericht Muenchen, HRB 153243,
Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill