[PATCH 51/64] tracing: Use struct_group() to zero struct trace_iterator

Kees Cook
2021-07-27T21:17:12Z

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct trace_iterator that should
be initialized to zero.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/trace_events.h | 26 ++++++++++++++------------
kernel/trace/trace.c | 4 +---
2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index ad413b382a3c..cadad77fe524 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -101,18 +101,20 @@ struct trace_iterator {
bool snapshot;

/* The below is zeroed out in pipe_read */
- struct trace_seq seq;
- struct trace_entry *ent;
- unsigned long lost_events;
- int leftover;
- int ent_size;
- int cpu;
- u64 ts;
-
- loff_t pos;
- long idx;
-
- /* All new field here will be zeroed out in pipe_read */
+ struct_group(init,
+ struct trace_seq seq;
+ struct trace_entry *ent;
+ unsigned long lost_events;
+ int leftover;
+ int ent_size;
+ int cpu;
+ u64 ts;
+
+ loff_t pos;
+ long idx;
+
+ /* All new field here will be zeroed out in pipe_read */
+ );
};

enum trace_iter_flags {
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c59dd35a6da5..9f83864b0be6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6691,9 +6691,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
cnt = PAGE_SIZE - 1;

/* reset all but tr, trace, and overruns */
- memset(&iter->seq, 0,
- sizeof(struct trace_iterator) -
- offsetof(struct trace_iterator, seq));
+ memset(&iter->init, 0, sizeof(iter->init));
cpumask_clear(iter->started);
trace_seq_init(&iter->seq);
iter->pos = -1;
--
2.30.2