Linux-libre 4.4-gnupck-4.4-gnu

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_intel_bts.c b/arch/x86/kernel/cpu/perf_event_intel_bts.c
index d1c0f254a..2cad71d1b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_bts.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_bts.c
@@ -495,6 +495,19 @@ static int bts_event_init(struct perf_event *event)
 	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
+	 * users on paranoid systems since it provides trace data
+	 * to the user in a zero-copy fashion.
+	 *
+	 * Note that the default paranoia setting permits unprivileged
+	 * users to profile the kernel.
+	 */
+	if (event->attr.exclude_kernel && perf_paranoid_kernel() &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
 	ret = x86_reserve_hardware();
 	if (ret) {
 		x86_del_exclusive(x86_lbr_exclusive_bts);