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

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Date:   Fri, 12 May 2023 15:09:19 +0000
From:   Chuck Lever III <chuck.lever@...cle.com>
To:     Azeem Shaikh <azeemshaikh38@...il.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



> On May 12, 2023, at 7:53 AM, Azeem Shaikh <azeemshaikh38@...il.com> wrote:
> 
> 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.


> [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>
> ---
> v1: https://lore.kernel.org/all/20230510220952.3507366-1-azeemshaikh38@gmail.com/
> 
> Changes in v2:
> - Use __assign_str instead of strscpy.
> - Added the Fixes tag.
> 
> fs/nfsd/trace.h |    6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> 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))
> );
> 
> TRACE_EVENT(nfsd_cb_setup_err,
> -- 
> 2.40.1.606.ga4b1b128d6-goog
> 
> 

--
Chuck Lever