linux-kernel - Re: [PATCH] NFSD: Replace all non-returning strlcpy with strscpy

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Message-ID: <CADmuW3W5=pyg5AF5UPbj-+8geyxn7zcjsTkOO+_r4FSpWJq8YQ@mail.gmail.com>
Date:   Fri, 12 May 2023 10:47:46 -0400
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Chuck Lever III <chuck.lever@...cle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jeff Layton <jlayton@...nel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] NFSD: Replace all non-returning strlcpy with strscpy

On Fri, May 12, 2023 at 10:38 AM Chuck Lever III <chuck.lever@...cle.com> wrote:
>
>
>
> > On May 12, 2023, at 7:30 AM, Azeem Shaikh <azeemshaikh38@...il.com> wrote:
> >
> > Thanks Chuck and Kees for the review.
> >
> >>> Actually netid should use the __string() and __assign_str()
> >>> macros rather than open-coding a string copy, I think.
> >
> > Do you mean something like this?
> >
> > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > index 4183819ea082..72a906a053dc 100644
> > --- a/fs/nfsd/trace.h
> > +++ b/fs/nfsd/trace.h
> > @@ -1365,19 +1365,19 @@ TRACE_EVENT(nfsd_cb_setup,
> >                __field(u32, cl_id)
> >                __field(unsigned long, authflavor)
> >                __sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
> > -               __array(unsigned char, netid, 8)
> > +               __string(netid, netid)
> >        ),
> >        TP_fast_assign(
> >                __entry->cl_boot = clp->cl_clientid.cl_boot;
> >                __entry->cl_id = clp->cl_clientid.cl_id;
> > -               strlcpy(__entry->netid, netid, sizeof(__entry->netid));
> > +               __assign_str(netid, netid);
> >                __entry->authflavor = authflavor;
> >                __assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
> >                                  clp->cl_cb_conn.cb_addrlen)
> >        ),
> >        TP_printk("addr=%pISpc client %08x:%08x proto=%s flavor=%s",
> >                __get_sockaddr(addr), __entry->cl_boot, __entry->cl_id,
> > -               __entry->netid, show_nfsd_authflavor(__entry->authflavor))
> > +               __get_str(netid), show_nfsd_authflavor(__entry->authflavor))
> > );
>
> Yes. I don't remember why I chose to open-code the string
> handling in here.
>
> I agree with Kees, also: __assign_str() needs to handle
> the memory accesses properly, and I had assumed it did
> that already. My bad. That IMO should be handled as a
> separate patch.

Thanks I'll send out a patch with the __assign_str replacement for now.
I'll wait for Kees and Steve to respond on how to fix the memory
access in __assign_str.

> >>> Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
> >
> > Ack.
>
> I agree that it's not a high priority backport. However,
> I expect those who want to use trace points on KASAN-
> enabled stable kernels might prefer to have the
> __assign_str fix in place, along with this one.
>
> So, I'm good with including Fixes: or leaving it off. Up
> to you!
>

Will include it :)