linux-kernel - Re: Q.: Why does tty_ioctl.c: set_termios return EINTR instead of ERESTARTSYS?

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Sat, 15 Oct 2011 10:55:01 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Godmar Back <godmar@...il.com>
CC:	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg KH <gregkh@...e.de>
Subject: Re: Q.: Why does tty_ioctl.c: set_termios return EINTR instead of
 ERESTARTSYS?

On 10/14/2011 06:52 PM, Godmar Back wrote:
> A student in my OS class noticed during their shell assignment that
> tcsetattr() is being interrupted with EINTR even though they had set
> SA_RESTART.
> 
> Upon taking a closer look, I noticed that
> drivers/char/tty_ioctl.c:set_termios(), which lies on the code path
> for the POSIX tcsetattr() function, returns -EINTR when a signal is
> pending. Consequently, the SA_RESTART flag is not honored and user
> code must check for and handle EINTR.
> 
> I don't immediately see what would prevent this system call from being
> restartable.
> 
> Is there a particular reason why it cannot be made restartable?

EINTR is used when there is no way to rollback already performed
actions. In this case, a flush could be performed. (This holds only for
TCSETSF, TCSETSF2 and similar.) So I think this is the reason we cannot
return ERESTARTSYS.

However I CCed tty fellows, they may have a different opinion.

regards,
-- 
js
suse labs
--
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/