linux-kernel - Perf map file ownership check

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Message-ID: <357ED2BF-5CA6-454B-B433-BC6F6542D105@fb.com>
Date:	Wed, 15 Jan 2014 16:41:49 +0000
From:	Gaurav Jain <gjain@...com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Pekka Enberg <penberg@....fi>, Ingo Molnar <mingo@...nel.org>,
	"acme@...hat.com" <acme@...hat.com>
Subject: Perf map file ownership check

981c125 introduced a permission check on perf map files such that perf only loads the map file if it has ownership. Pekka mentioned that this prevents the perf tool from injecting arbitrary symbols from potentially malicious source.

In our workload, the code generating the map file is running as a non-root user. However, the perf tool is run as root. As a result, the ownership check fails and the map file is not loaded.

This raises 2 questions:
1. Is the ownership check necessary? What are the security implications of using symbols from an arbitrary source? I thought these are simply displayed by the perf tool.
2. Is there a way to avoid the check? Possibly with a -f flag.

Thanks,

Gaurav--
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