linux-kernel - [PATCH v1 0/2] perf/x86/intel: Work around BTS leaking kernel addresses

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Message-Id: <1441030168-6853-1-git-send-email-alexander.shishkin@linux.intel.com>
Date:	Mon, 31 Aug 2015 17:09:26 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v1 0/2] perf/x86/intel: Work around BTS leaking kernel addresses

Hi Peter and Ingo,

This is a respin to address Ingo's comments: I replaced the awkward
address comparison against PAGE_OFFSET with a kernel_ip() in the first
patch and amended the wording in the second. The original story
follows.

Due to imprecise IP sampling, BTS may (and often does) leak kernel
addresses when kernel tracing is not even enabled, which results in
mostly syscall entry points and page_fault handler addresses being
exposed. This might be a security concern for the address
randomization, and it also makes life harder for gdb that makes use of
bts samples.

This patchset works around the old (DS) driver and disables the new
(intel_bts) for the unprivileged users on systems where perf paranoia
level prohibits kernel tracing.

Not sure if these should be treated as bugfixes.

Alexander Shishkin (2):
  perf/x86/intel/ds: Work around BTS leaking kernel addresses
  perf/x86/intel/bts: Disallow use by unprivileged users on paranoid
    systems

 arch/x86/kernel/cpu/perf_event_intel_bts.c | 13 ++++++++++
 arch/x86/kernel/cpu/perf_event_intel_ds.c  | 40 +++++++++++++++++++++++++-----
 2 files changed, 47 insertions(+), 6 deletions(-)

-- 
2.5.0

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