From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761336AbZENWvi (ORCPT ); Thu, 14 May 2009 18:51:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756752AbZENWmi (ORCPT ); Thu, 14 May 2009 18:42:38 -0400 Received: from kroah.org ([198.145.64.141]:52469 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756578AbZENWmU (ORCPT ); Thu, 14 May 2009 18:42:20 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Thu May 14 15:35:25 2009 Message-Id: <20090514223524.855079595@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Thu, 14 May 2009 15:33:03 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Steve French , Jeff Layton , Steve French , Suresh Jayaraman Subject: [patch 28/51] cifs: Fix unicode string area word alignment in session setup References: <20090514223235.348540705@mini.kroah.org> Content-Disposition: inline; filename=cifs-fix-unicode-string-area-word-alignment-in-session-setup.patch In-Reply-To: <20090514223755.GA27019@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.29-stable review patch. If anyone has any objections, please let us know. ------------------ From: Jeff Layton commit 27b87fe52baba0a55e9723030e76fce94fabcea4 refreshed. cifs: fix unicode string area word alignment in session setup The handling of unicode string area alignment is wrong. decode_unicode_ssetup improperly assumes that it will always be preceded by a pad byte. This isn't the case if the string area is already word-aligned. This problem, combined with the bad buffer sizing for the serverDomain string can cause memory corruption. The bad alignment can make it so that the alignment of the characters is off. This can make them translate to characters that are greater than 2 bytes each. If this happens we can overflow the allocation. Fix this by fixing the alignment in CIFS_SessSetup instead so we can verify it against the head of the response. Also, clean up the workaround for improperly terminated strings by checking for a odd-length unicode buffers and then forcibly terminating them. Finally, resize the buffer for serverDomain. Now that we've fixed the alignment, it's probably fine, but a malicious server could overflow it. A better solution for handling these strings is still needed, but this should be a suitable bandaid. Signed-off-by: Jeff Layton Signed-off-by: Steve French Cc: Suresh Jayaraman Signed-off-by: Greg Kroah-Hartman --- fs/cifs/sess.c | 44 +++++++++++++++++++++++--------------------- 1 file changed, 23 insertions(+), 21 deletions(-) --- a/fs/cifs/sess.c +++ b/fs/cifs/sess.c @@ -285,27 +285,26 @@ static int decode_unicode_ssetup(char ** int words_left, len; char *data = *pbcc_area; - - cFYI(1, ("bleft %d", bleft)); - - /* SMB header is unaligned, so cifs servers word align start of - Unicode strings */ - data++; - bleft--; /* Windows servers do not always double null terminate - their final Unicode string - in which case we - now will not attempt to decode the byte of junk - which follows it */ + /* + * Windows servers do not always double null terminate their final + * Unicode string. Check to see if there are an uneven number of bytes + * left. If so, then add an extra NULL pad byte to the end of the + * response. + * + * See section 2.7.2 in "Implementing CIFS" for details + */ + if (bleft % 2) { + data[bleft] = 0; + ++bleft; + } words_left = bleft / 2; /* save off server operating system */ len = UniStrnlen((wchar_t *) data, words_left); -/* We look for obvious messed up bcc or strings in response so we do not go off - the end since (at least) WIN2K and Windows XP have a major bug in not null - terminating last Unicode string in response */ if (len >= words_left) return rc; @@ -343,13 +342,10 @@ static int decode_unicode_ssetup(char ** return rc; kfree(ses->serverDomain); - ses->serverDomain = kzalloc(2 * (len + 1), GFP_KERNEL); /* BB FIXME wrong length */ - if (ses->serverDomain != NULL) { + ses->serverDomain = kzalloc((4 * len) + 2, GFP_KERNEL); + if (ses->serverDomain != NULL) cifs_strfromUCS_le(ses->serverDomain, (__le16 *)data, len, nls_cp); - ses->serverDomain[2*len] = 0; - ses->serverDomain[(2*len) + 1] = 0; - } data += 2 * (len + 1); words_left -= len + 1; @@ -702,12 +698,18 @@ CIFS_SessSetup(unsigned int xid, struct } /* BB check if Unicode and decode strings */ - if (smb_buf->Flags2 & SMBFLG2_UNICODE) + if (smb_buf->Flags2 & SMBFLG2_UNICODE) { + /* unicode string area must be word-aligned */ + if (((unsigned long) bcc_ptr - (unsigned long) smb_buf) % 2) { + ++bcc_ptr; + --bytes_remaining; + } rc = decode_unicode_ssetup(&bcc_ptr, bytes_remaining, - ses, nls_cp); - else + ses, nls_cp); + } else { rc = decode_ascii_ssetup(&bcc_ptr, bytes_remaining, ses, nls_cp); + } ssetup_exit: if (spnego_key) {