From: Oleg Nesterov <oleg@redhat.com>
To: Stas Sergeev <stsp@list.ru>
Cc: Linux kernel <linux-kernel@vger.kernel.org>,
linux-api@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Amanieu d'Antras" <amanieu@gmail.com>,
Richard Weinberger <richard@nod.at>, Tejun Heo <tj@kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Jason Low <jason.low2@hp.com>,
Heinrich Schuchardt <xypron.glpk@gmx.de>,
Andrea Arcangeli <aarcange@redhat.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Josh Triplett <josh@joshtriplett.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Aleksa Sarai <cyphar@cyphar.com>, Paul Moore <pmoore@redhat.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Vladimir Davydov <vdavydov@parallels.com>
Subject: Re: [PATCH 4/4] sigaltstack: allow disabling and re-enabling sas within sighandler
Date: Mon, 1 Feb 2016 19:04:43 +0100 [thread overview]
Message-ID: <20160201180443.GA21064@redhat.com> (raw)
In-Reply-To: <56AF955D.7060601@list.ru>
On 02/01, Stas Sergeev wrote:
>
> 01.02.2016 20:09, Oleg Nesterov пишет:
> >OK, I didn't notice you modified save_altstack_ex() to use ->sas_ss_flags instead
> >of sas_ss_flags()... still doesn't look right, in this case restore_altstack() will
> >not restore sas_ss_size/sas_ss_sp and they can be changed by signal handler.
> How?
> Trying to change them in a sighandler with sigaltstack()
> will get EPERM.
Only if on_sig_stack() and this is not true if we change the stack.
> >Anyway, whatever I missed I agree with Andy, SS_FORCE looks simpler and better to me.
>
> But perhaps you missed the most important thing, that
> it is not possible to change the altstack in sighandler - you'll
> get EPERM, even with my patch.
See above.
> But with SS_FORCE this is
> exactly not the case.
Yes, and SS_FORCE means "I know what I do", looks very simple.
> Also it would be interesting to know what do you think about
> just removing the EPERM check instead of this all.
I won't argue, but to me it would be better to keep this EPERM if !force.
Just because we should avoid the incompatible changes if possible.
Oleg.
next prev parent reply other threads:[~2016-02-01 18:04 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-31 16:16 [PATCH 0/4] make sigaltstack() compatible with swapcontext() Stas Sergeev
2016-01-31 16:18 ` [PATCH 1/4] selftests: Add test for sigaltstack(SS_DISABLE) inside sighandler Stas Sergeev
2016-02-12 16:12 ` Shuah Khan
2016-02-12 16:17 ` Stas Sergeev
2016-01-31 16:21 ` [PATCH 2/4] score: signal: fix sigaltstack check Stas Sergeev
2016-02-02 19:07 ` Lennox Wu
2016-01-31 16:24 ` [PATCH 3/4] x86: signal: unify the sigaltstack check with other arches Stas Sergeev
2016-01-31 16:58 ` Andy Lutomirski
2016-01-31 18:03 ` Stas Sergeev
2016-01-31 16:28 ` [PATCH 4/4] sigaltstack: allow disabling and re-enabling sas within sighandler Stas Sergeev
2016-01-31 17:00 ` Andy Lutomirski
2016-01-31 17:33 ` Stas Sergeev
2016-01-31 19:03 ` Andy Lutomirski
2016-01-31 20:08 ` Stas Sergeev
2016-01-31 20:11 ` Andy Lutomirski
2016-01-31 22:36 ` Stas Sergeev
2016-01-31 22:44 ` Andy Lutomirski
2016-01-31 23:45 ` Stas Sergeev
2016-02-01 16:06 ` Oleg Nesterov
2016-02-01 16:57 ` Stas Sergeev
2016-02-01 17:27 ` Oleg Nesterov
2016-02-01 17:09 ` Oleg Nesterov
2016-02-01 17:26 ` Stas Sergeev
2016-02-01 18:04 ` Oleg Nesterov [this message]
2016-02-01 18:16 ` Stas Sergeev
2016-02-01 18:28 ` Andy Lutomirski
2016-02-01 18:40 ` Stas Sergeev
2016-02-01 18:52 ` Oleg Nesterov
2016-02-01 19:01 ` Stas Sergeev
2016-02-01 19:29 ` Oleg Nesterov
2016-02-01 19:46 ` Stas Sergeev
2016-02-01 20:41 ` Oleg Nesterov
2016-02-01 23:06 ` Stas Sergeev
-- strict thread matches above, loose matches on Subject: below --
2016-01-31 19:10 [PATCH v2 0/4] make sigaltstack() compatible with swapcontext() Stas Sergeev
2016-01-31 19:18 ` [PATCH 4/4] sigaltstack: allow disabling and re-enabling sas within sighandler Stas Sergeev
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