Re: [PATCH v2 50/63] tracing: Use memset_startat() to zero struct trace_iterator
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-08-18 13:33:57
Also in:
dri-devel, linux-block, linux-hardening, linux-kbuild, linux-staging, lkml, netdev
On Tue, 17 Aug 2021 23:05:20 -0700 Kees Cook [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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);
I can't find memset_startat() in mainline nor linux-next. I don't see it in this thread either, but since this has 63 patches, I could have easily missed it. This change really should belong to a patch set that just introduces memset_startat() (and perhaps memset_after()) and then updates all the places that should use it. That way I can give it a proper review. In other words, you should break this patch set up into smaller, more digestible portions for the reviewers. Thanks, -- Steve
cpumask_clear(iter->started); trace_seq_init(&iter->seq); iter->pos = -1;