linux-kernel - Re: eBPF verifier thoughts (Re: [PATCH v15 net-next 00/11] eBPF syscall, verifier, testsuite)

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 for Android: free password hash cracker in your pocket

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

Message-ID: <CAMEtUuzQF+3uWFWmj5nSdYoJfo0W2F0wkvoyc4pP--EH3O_jYA@mail.gmail.com>
Date:	Fri, 26 Sep 2014 15:26:40 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	David Miller <davem@...emloft.net>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: eBPF verifier thoughts (Re: [PATCH v15 net-next 00/11] eBPF
 syscall, verifier, testsuite)

On Fri, Sep 26, 2014 at 3:07 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Fri, Sep 26, 2014 at 3:03 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>> On Fri, Sep 26, 2014 at 2:47 PM, Andy Lutomirski <luto@...capital.net> wrote:
>>>
>>> Can't you just disallow the 1-byte write to the stack?
>>
>> of course not.
>> That would be extremely limiting to users.
>> Can you actually see yourself living with stack that only
>> allows 8-byte writes/reads?
>> The stack usage will increase a lot, since all char/short
>> stack variables will become 8-byte...
>
> How about requiring that sub-8-byte stack accesses only be to integer slots?

you mean to reject the sub-8-byte write early if it's going
into space where pointers were stored?
That will limit stack reuse.
gcc/llvm generate code where the same stack location
is used by different variables during life of the function.
So if I reject the write early, it will break otherwise valid
programs.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/