linux-kernel - O_NONBLOCK setting "leak" outside of a process??

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-next>] [day] [month] [year] [list]

Message-Id: <200701272152.11087.vda.linux@googlemail.com>
Date:	Sat, 27 Jan 2007 21:52:11 +0100
From:	Denis Vlasenko <vda.linux@...glemail.com>
To:	linux-kernel@...r.kernel.org
Subject: O_NONBLOCK setting "leak" outside of a process??

Hi,

I am currently on Linux 2.6.18, x86_64.
I came across strange behavior while working on one
of busybox applets. I narrowed it down to these two
trivial testcases:

#include <unistd.h>
#include <fcntl.h>
int main() {
        fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
        return 0;
}

#include <unistd.h>
#include <fcntl.h>
int main() {
        fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) & ~O_NONBLOCK);
        return 0;
}

If I run "nonblock" in Midnight Commander in KDE's Konsole,
screen redraw starts to work ~5 times slower. For example,
Ctrl-O ("show/hide panels" in MC) takes ~0.5 sec to redraw.
This persists after the program exist (which it
does immediately as you see).
Running "block" reverts things to normal.

I mean: how can O_NONBLOCK _issued in a process which
already exited_ have any effect whatsoever on MC or Konsole?
They can't even know that it did it, right?

Either I do not know something subtle about Unix or some sort
of bug is at work.

Any advice?
--
vda
-
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/