tracing: Do not set trace clock if tracefs lockdown is in effect
commit5.4-rM2-2.2.x-imx-squashedbf24daac8f
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:17911ff38a
("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>
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67551f9584
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07af0d03e8
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@ -9270,6 +9270,11 @@ __init static int tracing_set_default_clock(void)
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{
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/* sched_clock_stable() is determined in late_initcall */
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if (!trace_boot_clock && !sched_clock_stable()) {
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if (security_locked_down(LOCKDOWN_TRACEFS)) {
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pr_warn("Can not set tracing clock due to lockdown\n");
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return -EPERM;
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}
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printk(KERN_WARNING
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"Unstable clock detected, switching default tracing clock to \"global\"\n"
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"If you want to keep using the local clock, then add:\n"
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