[PATCH v2 50/63] tracing: Use memset_startat() to zero struct trace_iterator

Kees Cook
2021-08-18T06:17:01Z

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

Use memset_startat() to avoid confusing memset() about writing beyond
the target struct member.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
kernel/trace/trace.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 13587e771567..9ff8c31975cd 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_startat(iter, 0, seq);
cpumask_clear(iter->started);
trace_seq_init(&iter->seq);
iter->pos = -1;
--
2.30.2