From 2eece390bf68ec8f733d7e4a3ba8a5ea350082ae Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Mon, 23 Oct 2017 15:35:33 +0300 Subject: [PATCH] perf/x86/intel/bts: Fix exclusive event reference leak Commit: d2878d642a4ed ("perf/x86/intel/bts: Disallow use by unprivileged users on paranoid systems") ... adds a privilege check in the exactly wrong place in the event init path: after the 'LBR exclusive' reference has been taken, and doesn't release it in the case of insufficient privileges. After this, nobody in the system gets to use PT or LBR afterwards. This patch moves the privilege check to where it should have been in the first place. Signed-off-by: Alexander Shishkin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: d2878d642a4ed ("perf/x86/intel/bts: Disallow use by unprivileged users on paranoid systems") Link: http://lkml.kernel.org/r/20171023123533.16973-1-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/events/intel/bts.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c index 16076eb34699..141e07b06216 100644 --- a/arch/x86/events/intel/bts.c +++ b/arch/x86/events/intel/bts.c @@ -546,9 +546,6 @@ static int bts_event_init(struct perf_event *event) if (event->attr.type != bts_pmu.type) return -ENOENT; - if (x86_add_exclusive(x86_lbr_exclusive_bts)) - return -EBUSY; - /* * BTS leaks kernel addresses even when CPL0 tracing is * disabled, so disallow intel_bts driver for unprivileged @@ -562,6 +559,9 @@ static int bts_event_init(struct perf_event *event) !capable(CAP_SYS_ADMIN)) return -EACCES; + if (x86_add_exclusive(x86_lbr_exclusive_bts)) + return -EBUSY; + ret = x86_reserve_hardware(); if (ret) { x86_del_exclusive(x86_lbr_exclusive_bts); -- 2.20.1