From: Masami Ichikawa masami256@gmail.com
commit bf24daac8f2bd5b8affaec03c2be1d20bcdd6837 upstream.
When trace_clock option is not set and unstable clcok detected, tracing_set_default_clock() sets trace_clock(ThinkPad A285 is one of case). In that case, if lockdown is in effect, null pointer dereference error happens in ring_buffer_set_clock().
Link: http://lkml.kernel.org/r/20200116131236.3866925-1-masami256@gmail.com
Cc: stable@vger.kernel.org Fixes: 17911ff38aa58 ("tracing: Add locked_down checks to the open calls of files created for tracefs") Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1788488 Signed-off-by: Masami Ichikawa masami256@gmail.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9270,6 +9270,11 @@ __init static int tracing_set_default_cl { /* sched_clock_stable() is determined in late_initcall */ if (!trace_boot_clock && !sched_clock_stable()) { + if (security_locked_down(LOCKDOWN_TRACEFS)) { + pr_warn("Can not set tracing clock due to lockdown\n"); + return -EPERM; + } + printk(KERN_WARNING "Unstable clock detected, switching default tracing clock to "global"\n" "If you want to keep using the local clock, then add:\n"