On Wed, Aug 18, 2021 at 09:33:49AM -0400, Steven Rostedt wrote:
On Tue, 17 Aug 2021 23:05:20 -0700 Kees Cook keescook@chromium.org wrote:
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);
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.
Sorry, it isn't called out in the Subject, but it's part of this patch: https://lore.kernel.org/lkml/20210818060533.3569517-38-keescook@chromium.org...
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.
I will split memset_after() and memset_startat() introduction patches. I already split up each use into individual cases, so that those changes could be checked one step at a time for differences in pahole struct layout and object code.
Thanks for taking a look!
-Kees