Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753132Ab2HTSl6 (ORCPT ); Mon, 20 Aug 2012 14:41:58 -0400 Received: from smtpfb1-g21.free.fr ([212.27.42.9]:34897 "EHLO smtpfb1-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750775Ab2HTSl4 (ORCPT ); Mon, 20 Aug 2012 14:41:56 -0400 From: Jim Meyering To: linux-kernel@vger.kernel.org Cc: Steve French , linux-cifs@vger.kernel.org, samba-technical@lists.samba.org Subject: Re: [PATCH] cifs: remove misleading strncpy: each name has length < 16 In-Reply-To: <1345481724-30108-6-git-send-email-jim@meyering.net> (Jim Meyering's message of "Mon, 20 Aug 2012 18:55:24 +0200") References: <1345481724-30108-1-git-send-email-jim@meyering.net> <1345481724-30108-6-git-send-email-jim@meyering.net> Date: Mon, 20 Aug 2012 20:41:12 +0200 Message-ID: <87zk5pl83b.fsf@rho.meyering.net> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1697 Lines: 39 Jim Meyering wrote: > From: Jim Meyering > > Each of the protocols[i].name strings (statically declared above) > has length less than 16, so this use of strncpy is misleading: > strncpy(pSMB->DialectsArray+count, protocols[i].name, 16); > Besides, if a new name were added with length N >= 16, the existing > strncpy-using code would be buggy, creating a ->DialectsArray buffer > containing N-16+1 unset bytes where the NUL terminator should have > been. Instead, traverse the name only once go get its length, s/go/to/, of course. > use a BUG_ON assertion to enforce the length restriction > and use memcpy to perform the copy. > > Signed-off-by: Jim Meyering > --- > fs/cifs/cifssmb.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c > index 074923c..16a9018 100644 > --- a/fs/cifs/cifssmb.c > +++ b/fs/cifs/cifssmb.c > @@ -441,8 +441,10 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses) > > count = 0; > for (i = 0; i < CIFS_NUM_PROT; i++) { > - strncpy(pSMB->DialectsArray+count, protocols[i].name, 16); > - count += strlen(protocols[i].name) + 1; > + size_t len = strlen(protocols[i].name); > + BUG_ON(len >= 16); > + memcpy(pSMB->DialectsArray+count, protocols[i].name, len + 1); > + count += len + 1; > /* null at end of source and target buffers anyway */ > } > inc_rfc1001_len(pSMB, count); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/