[PATCH 5.10 063/120] tracepoint: Fix race between tracing and removing tracepoint

Greg Kroah-Hartman
2021-02-08T17:28:24Z

From: Alexey Kardashevskiy <aik@ozlabs.ru>

commit c8b186a8d54d7e12d28e9f9686cb00ff18fc2ab2 upstream.

When executing a tracepoint, the tracepoint's func is dereferenced twice -
in __DO_TRACE() (where the returned pointer is checked) and later on in
__traceiter_##_name where the returned pointer is dereferenced without
checking which leads to races against tracepoint_removal_sync() and
crashes.

This adds a check before referencing the pointer in tracepoint_ptr_deref.

Link: https://lkml.kernel.org/r/20210202072326.120557-1-aik@ozlabs.ru

Cc: stable@vger.kernel.org
Fixes: d25e37d89dd2f ("tracepoint: Optimize using static_call()")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/tracepoint.h | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -307,11 +307,13 @@ static inline struct tracepoint *tracepo
\
it_func_ptr = \
rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
- do { \
- it_func = (it_func_ptr)->func; \
- __data = (it_func_ptr)->data; \
- ((void(*)(void *, proto))(it_func))(__data, args); \
- } while ((++it_func_ptr)->func); \
+ if (it_func_ptr) { \
+ do { \
+ it_func = (it_func_ptr)->func; \
+ __data = (it_func_ptr)->data; \
+ ((void(*)(void *, proto))(it_func))(__data, args); \
+ } while ((++it_func_ptr)->func); \
+ } \
return 0; \
} \
DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);