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

[Mathieu Desnoyers]

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@xxxxxxxxxxxxx>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Michael Jeanson <mjeanson@xxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Jordan Rife <jrife@xxxxxxxxxx>
---
 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