1 files changed, 13 insertions, 2 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 7fb16d90e7b1..f64fbaae781a 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -637,12 +637,20 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
  *      pc = preempt_count();
  *
  *      __data_size = ftrace_get_offsets_<call>(&__data_offsets, args);
- *      __entry_size = __data_size + sizeof(*entry);
+ *
+ *      // Below we want to get the aligned size by taking into account
+ *      // the u32 field that will later store the buffer size
+ *      __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),
+ *                           sizeof(u64));
+ *      __entry_size -= sizeof(u32);
  *
  *      do {
  *              char raw_data[__entry_size]; <- allocate our sample in the stack
  *              struct trace_entry *ent;
  *
+ *              zero dead bytes from alignment to avoid stack leak to userspace:
+ *
+ *              *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;
  *              entry = (struct ftrace_raw_<call> *)raw_data;
  *              ent = &entry->ent;
  *              tracing_generic_entry_update(ent, irq_flags, pc);
@@ -685,12 +693,15 @@ static void ftrace_profile_##call(proto)				\
         pc = preempt_count();                                           \
                                                                         \
         __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
-        __entry_size = ALIGN(__data_size + sizeof(*entry), sizeof(u64));\
+        __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
+                             sizeof(u64));                              \
+        __entry_size -= sizeof(u32);                                    \
                                                                         \
         do {                                                            \
                 char raw_data[__entry_size];                            \
                 struct trace_entry *ent;                                \
                                                                         \
+                *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL; \
                 entry = (struct ftrace_raw_##call *)raw_data;           \
                 ent = &entry->ent;                                      \
                 tracing_generic_entry_update(ent, irq_flags, pc);       \