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@xxxxxxxxxxxx> 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@xxxxxxxxxxx> > > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > --- > > 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@xxxxxxxxxxxx/ > 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 -- Kees Cook
