From: Stas Sergeev <stsp-cmBhpYW9OiY@public.gmane.org>
To: Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
Aleksa Sarai <cyphar-gVpy/LI/lHzQT0dZR+AlfA@public.gmane.org>,
Amanieu d'Antras
<amanieu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Andrea Arcangeli
<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Eric W. Biederman"
<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
Frederic Weisbecker
<fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>,
Jason Low <jason.low2-VXdhtT5mjnY@public.gmane.org>,
Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>,
Konstantin Khlebnikov
<khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Palmer Dabbelt <palmer-96lFi9zoCfxBDgjK7y7TUQ@public.gmane.org>,
Paul Moore <pmoore-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH 1/4] signals/sigaltstack: If SS_AUTODISARM, bypass on_sig_stack
Date: Sat, 7 May 2016 17:37:41 +0300 [thread overview]
Message-ID: <0081b876-033b-4fb7-3daf-d38b2df1fda6@list.ru> (raw)
In-Reply-To: <c46bee4654ca9e68c498462fd11746e2bd0d98c8.1462296606.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
03.05.2016 20:31, Andy Lutomirski пишет:
> If a signal stack is set up with SS_AUTODISARM, then the kernel
> inherently avoids incorrectly resetting the signal stack if signals
> recurse: the signal stack will be reset on the first signal
> delivery. This means that we don't need check the stack pointer
> when delivering signals if SS_AUTODISARM is set.
>
> This will make segmented x86 programs more robust: currently there's
> a hole that could be triggered if ESP/RSP appears to point to the
> signal stack but actually doesn't due to a nonzero SS base.
>
> Signed-off-by: Stas Sergeev <stsp-cmBhpYW9OiY@public.gmane.org>
> Cc: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
> Cc: Aleksa Sarai <cyphar-gVpy/LI/lHzQT0dZR+AlfA@public.gmane.org>
> Cc: Amanieu d'Antras <amanieu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Andrea Arcangeli <aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> Cc: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
> Cc: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
> Cc: Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
> Cc: Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: H. Peter Anvin <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
> Cc: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
> Cc: Jason Low <jason.low2-VXdhtT5mjnY@public.gmane.org>
> Cc: Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>
> Cc: Konstantin Khlebnikov <khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org>
> Cc: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> Cc: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Palmer Dabbelt <palmer-96lFi9zoCfxBDgjK7y7TUQ@public.gmane.org>
> Cc: Paul Moore <pmoore-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
> Cc: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
> Cc: Richard Weinberger <richard-/L3Ra7n9ekc@public.gmane.org>
> Cc: Sasha Levin <sasha.levin-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Cc: Shuah Khan <shuahkh-JPH+aEBZ4P+UEJcrhfAQsw@public.gmane.org>
> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
> Cc: Vladimir Davydov <vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
> Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Signed-off-by: Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> ---
> include/linux/sched.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 2950c5cd3005..8f03a93348b9 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2576,6 +2576,18 @@ static inline int kill_cad_pid(int sig, int priv)
> */
> static inline int on_sig_stack(unsigned long sp)
> {
> + /*
> + * If the signal stack is AUTODISARM then, by construction, we
> + * can't be on the signal stack unless user code deliberately set
> + * SS_AUTODISARM when we were already on the it.
"on the it" -> "on it".
Anyway, I am a bit puzzled with this patch.
You say "unless user code deliberately set
SS_AUTODISARM when we were already on the it"
so what happens in case it actually does?
Without your patch: if user sets up the same sas - no stack switch.
if user sets up different sas - stack switch on nested signal.
With your patch: stack switch in any case, so if user
set up same sas - stack corruption by nested signal.
Or am I missing the intention?
next prev parent reply other threads:[~2016-05-07 14:37 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1462296606.git.luto@kernel.org>
2016-05-03 17:31 ` [PATCH 1/4] signals/sigaltstack: If SS_AUTODISARM, bypass on_sig_stack Andy Lutomirski
[not found] ` <c46bee4654ca9e68c498462fd11746e2bd0d98c8.1462296606.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-05-04 6:32 ` Ingo Molnar
[not found] ` <20160504063233.GB9499-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-05-04 23:02 ` Andy Lutomirski
2016-05-07 14:37 ` Stas Sergeev [this message]
2016-05-09 1:32 ` Andy Lutomirski
[not found] ` <CALCETrX4AMCUkYMXe6-RoHTHQ=bpunM5keHSxMg=fEVtb1EmqA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-05-09 2:04 ` Stas Sergeev
[not found] ` <97f8e27a-019c-a5d4-2d2c-c2a9627cf23d-cmBhpYW9OiY@public.gmane.org>
2016-05-14 4:18 ` Andy Lutomirski
[not found] ` <CALCETrV+gmXn-kTJmKBDPM8HaRTcvp+eGmeF7mOES6bCje2AGQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-05-14 11:18 ` Stas Sergeev
2016-05-14 16:35 ` Andy Lutomirski
2016-05-03 17:31 ` [PATCH 2/4] selftests/sigaltstack: Fix the sas test on old kernels Andy Lutomirski
[not found] ` <f3e739bf435beeaecbd5f038f1359d2eac6d1e63.1462296606.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-05-07 15:02 ` Stas Sergeev
[not found] ` <abedee05-5671-7ba7-c256-41e61fb596cb-cmBhpYW9OiY@public.gmane.org>
2016-05-09 1:32 ` Andy Lutomirski
2016-05-03 17:31 ` [PATCH 3/4] signals/sigaltstack: Report current flag bits in sigaltstack() Andy Lutomirski
[not found] ` <94b291ec9fd47741a9264851e316e158ded0b00d.1462296606.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-05-04 6:33 ` Ingo Molnar
2016-05-03 17:31 ` [PATCH 4/4] signals/sigaltstack: Change SS_AUTODISARM to (1U << 31) Andy Lutomirski
[not found] ` <bb996508a600af14b406810c3d58fe0e0d0afe0d.1462296606.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-05-07 15:16 ` Stas Sergeev
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