linux-kernel - [RFC PATCH v2] compat: poll() in 32-bit applications does not handle negative timeout values properly on 64-bit kernels

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Date:	Fri, 10 Feb 2012 23:54:49 -0600
From:	Josh Hunt <johunt@...mai.com>
To:	Al Viro <viro@...IV.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, arnd@...db.de, linux-arch@...r.kernel.org
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH v2] compat: poll() in 32-bit applications does not handle
 negative timeout values properly on 64-bit kernels

We have hit an issue where our 32-bit applications using poll() and
passing in a value of -1 for the timeout value return after ~49 days
(2^32 msec), instead of waiting indefinitely. I've instrumented the
kernel and found we are hitting the case where poll() believes we've
passed in a positive number and thus creates a timespec, etc. I've
implemented compat_sys_poll() to sign-extend the timeout value and
resolve the issue.

There was an almost identical patch submitted last year, but for
whatever reason did not make it in:
https://lkml.org/lkml/2011/9/18/19

I am guessing there are other architectures affected by this bug. This
patch only fixes x86.

Josh

View attachment "compat-sys-poll.patch" of type "text/x-patch" (2340 bytes)