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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Jiri Slaby <jslaby@suse.cz>, Arseny Maslennikov <ar@cs.msu.ru>,
	linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
	Rob Landley <rob@landley.net>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Pavel Machek <pavel@ucw.cz>,
	linux-api@vger.kernel.org,
	"Vladimir D. Seleznev" <vseleznv@altlinux.org>
Subject: Re: [PATCH v3 4/7] linux/signal.h: Ignore SIGINFO by default in new tasks
Date: Thu, 30 Apr 2020 09:19:52 +0200	[thread overview]
Message-ID: <20200430071952.GA2411804@kroah.com> (raw)
In-Reply-To: <20200430071437.x3ilwkh3lyf4iq6u@wittgenstein>

On Thu, Apr 30, 2020 at 09:14:37AM +0200, Christian Brauner wrote:
> On Thu, Apr 30, 2020 at 08:53:56AM +0200, Jiri Slaby wrote:
> > On 30. 04. 20, 8:42, Arseny Maslennikov wrote:
> > > This matches the behaviour of other Unix-like systems that have SIGINFO
> > > and causes less harm to processes that do not install handlers for this
> > > signal, making the keyboard status character non-fatal for them.
> > > 
> > > This is implemented with the assumption that SIGINFO is defined
> > > to be equivalent to SIGPWR; still, there is no reason for PWR to
> > > result in termination of the signal recipient anyway — it does not
> > > indicate there is a fatal problem with the recipient's execution
> > > context (like e.g. FPE/ILL do), and we have TERM/KILL for explicit
> > > termination requests.
> > > 
> > > To put it another way:
> > > The only scenario where system behaviour actually changes is when the
> > > signal recipient has default disposition for SIGPWR. If a process
> > > chose to interpret a SIGPWR as an incentive to cleanly terminate, it
> > > would supply its own handler — and this commit does not affect processes
> > > with non-default handlers.
> > > 
> > > Signed-off-by: Arseny Maslennikov <ar@cs.msu.ru>
> > > ---
> > >  include/linux/signal.h | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/linux/signal.h b/include/linux/signal.h
> > > index 05bacd2ab..dc31da8fc 100644
> > > --- a/include/linux/signal.h
> > > +++ b/include/linux/signal.h
> > > @@ -369,7 +369,7 @@ extern bool unhandled_signal(struct task_struct *tsk, int sig);
> > >   *	|  SIGSYS/SIGUNUSED  |	coredump 	|
> > >   *	|  SIGSTKFLT         |	terminate	|
> > >   *	|  SIGWINCH          |	ignore   	|
> > > - *	|  SIGPWR            |	terminate	|
> > > + *	|  SIGPWR            |	ignore   	|
> > 
> > You need to update signal.7 too:
> > https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man7/signal.7#n285
> 
> (I fail this whole thread via b4 and it appears that a bunch of messages
> are missing on lore. Might just be delay though.)
> 
> How this is this not going to break userspace?

That's my main hesitation for taking this patchset.

> Just for a start, SIGPWR (for better or worse) was used for a long time
> by some sandboxing/container runtimes to shutdown a process and still
> is.

That's a good reason to not do this :(

greg k-h

  reply	other threads:[~2020-04-30  7:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30  6:42 [PATCH v3 0/7] TTY Keyboard Status Request Arseny Maslennikov
2020-04-30  6:42 ` [PATCH v3 1/7] signal.h: Define SIGINFO on all architectures Arseny Maslennikov
2020-04-30  6:42 ` [PATCH v3 2/7] tty: termios: Reserve space for VSTATUS in .c_cc Arseny Maslennikov
2020-04-30  6:42 ` [PATCH v3 3/7] n_tty: Send SIGINFO to fg pgrp on status request character Arseny Maslennikov
2020-04-30  6:42 ` [PATCH v3 4/7] linux/signal.h: Ignore SIGINFO by default in new tasks Arseny Maslennikov
2020-04-30  6:53   ` Jiri Slaby
2020-04-30  7:14     ` Christian Brauner
2020-04-30  7:19       ` Greg Kroah-Hartman [this message]
2020-04-30  7:37       ` Aleksa Sarai
2020-04-30  8:00         ` Christian Brauner
2020-04-30  6:42 ` [PATCH v3 5/7] tty: Add NOKERNINFO lflag to termios Arseny Maslennikov
2020-04-30  6:55   ` Jiri Slaby
2020-04-30  7:20     ` Arseny Maslennikov
2020-04-30  6:43 ` [PATCH v3 6/7] n_tty: ->ops->write: Cut core logic out to a separate function Arseny Maslennikov
2020-04-30  6:43 ` [PATCH v3 7/7] n_tty: Provide an informational line on VSTATUS receipt Arseny Maslennikov
2020-04-30  7:29   ` Jiri Slaby
2020-04-30  9:08     ` Arseny Maslennikov

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