linux-kernel - Re: [PATCH 1/1] tty: set_termios/set

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Message-ID: <20130129194908.GA29480@redhat.com>
Date:	Tue, 29 Jan 2013 20:49:08 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lingzhu Xiang <lxiang@...hat.com>,
	Roman Rakus <rrakus@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] tty: set_termios/set_termiox should not return
	-EINTR

On 01/29, Jiri Slaby wrote:
>
> On 01/29/2013 08:07 PM, Oleg Nesterov wrote:
> >
> > Change set_termios/set_termiox to return -ERESTARTSYS to fix this
> > particular problem.
>
> This looks reasonable. However given the link above says:
>  You are not authorized to access bug #904907.
> the description above is poor. What problem exactly does this fix?

A syscall must never return EINTR unless it can not be restarted
(or it should not be restarted by, say, historical reasons).

In this case ioctl(TCSETAW) returns -EINTR even if it is interrupted
by the signal which has the SA_RESTART handler. This doesn't look right
no matter what.

> Why this should go to stable at all?

OK, this is up to you.

But if this patch is correct, perhaps it should be backported. This
-EINTR breaks /bin/bash which doesn't expect it, this leads to
"*** glibc detected *** ./bash-4.1.2-14.el6/bin/bash: double free or corruption (out):"

Perhaps /bin/bash is buggy too, I do not know. Probably Roman and
Lingzhu can tell more.

Oleg.

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