[RFC PATCH v4 4/4] tracing: Add might_fault() check in __DO_TRACE() for syscall

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Catch incorrect use of syscall tracepoints even if no probes are
registered by adding a might_fault() check in __DO_TRACE() when
syscall=1.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jordan Rife <jrife@google.com>
---
 include/linux/tracepoint.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 259f0ab4ece6..7bed499b7055 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -226,10 +226,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 		if (!(cond))						\
 			return;						\
 									\
-		if (syscall)						\
+		if (syscall) {						\
 			rcu_read_lock_trace();				\
-		else							\
+			might_fault();					\
+		} else {						\
 			preempt_disable_notrace();			\
+		}							\
 									\
 		__DO_TRACE_CALL(name, TP_ARGS(args));			\
 									\
-- 
2.39.5