linux-hardening - Re: [PATCH v2] NFSD: Remove all occurences of strlcpy

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Date:   Fri, 12 May 2023 16:34:54 -0400
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Chuck Lever III <chuck.lever@...cle.com>
Cc:     Jeff Layton <jlayton@...nel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] NFSD: Remove all occurences of strlcpy

Resending as plain text.

> >> strlcpy() reads the entire source buffer first.
> >> This read may exceed the destination size limit.
> >> This is both inefficient and can lead to linear read
> >> overflows if a source string is not NUL-terminated [1].
> >> In an effort to remove strlcpy() completely [2], replace
> >> strlcpy here.
> >
> > Let's update the patch description. This change is really
> > a clean up -- it doesn't address the memory issues you
> > originally described.
>
> Unless, of course, you intend to apply this patch /after/
> a patch that fixes __assign_str(). In that case, no change
> to the patch description is needed.

No, I plan to land this patch before attempting to fix __assign_str itself.
Let me know if the below description looks good to you and I'll send
over a v3 patch:

[PATCH v3] NFSD: Remove open coding of string copy

Instead of open coding a __dynamic_array(), use the __string() and
__assign_str()
helper macros that exist for this kind of use case.

Part of an effort to remove deprecated strlcpy() [1] completely from the
kernel[2].

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>