Re: [RFC PATCH v4 4/4] tracing: Add might_fault() check in __DO_TRACE() for syscall
From: Mathieu Desnoyers
Date: Mon Oct 28 2024 - 15:59:58 EST
On 2024-10-28 15:09, Mathieu Desnoyers wrote:
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(); \
Actually, __DO_TRACE() is not the best place to put this, because it's
only executed when the tracepoint is enabled.
I'll move this to __DECLARE_TRACE_SYSCALL()
#define __DECLARE_TRACE_SYSCALL(name, proto, args, cond, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
static inline void trace_##name(proto) \
{ \
might_fault(); \
if (static_branch_unlikely(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
TP_CONDITION(cond), 1); \
[...]
instead in v5.
Thanks,
Mathieu
+ } else { \
preempt_disable_notrace(); \
+ } \
\
__DO_TRACE_CALL(name, TP_ARGS(args)); \
\
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com