From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753123AbdF0LON (ORCPT ); Tue, 27 Jun 2017 07:14:13 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34853 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752743AbdF0LMj (ORCPT ); Tue, 27 Jun 2017 07:12:39 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "=?UTF-8?Q?=E7=9F=B3=E7=A3=8A?=" , "David S. Miller" , "David Howells" , "Dan Carpenter" , "Marc Dionne" Date: Tue, 27 Jun 2017 12:10:34 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 6/7] rxrpc: Fix several cases where a padded len isn't checked in ticket decode In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.45-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: David Howells commit 5f2f97656ada8d811d3c1bef503ced266fcd53a0 upstream. This fixes CVE-2017-7482. When a kerberos 5 ticket is being decoded so that it can be loaded into an rxrpc-type key, there are several places in which the length of a variable-length field is checked to make sure that it's not going to overrun the available data - but the data is padded to the nearest four-byte boundary and the code doesn't check for this extra. This could lead to the size-remaining variable wrapping and the data pointer going over the end of the buffer. Fix this by making the various variable-length data checks use the padded length. Reported-by: 石磊 Signed-off-by: David Howells Reviewed-by: Marc Dionne Reviewed-by: Dan Carpenter Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust filename, context] Signed-off-by: Ben Hutchings --- net/rxrpc/ar-key.c | 64 ++++++++++++++++++++++++++++++--------------------------- 1 file changed, 34 insertions(+), 30 deletions(-) --- a/net/rxrpc/ar-key.c +++ b/net/rxrpc/ar-key.c @@ -213,7 +213,7 @@ static int rxrpc_krb5_decode_principal(s unsigned int *_toklen) { const __be32 *xdr = *_xdr; - unsigned int toklen = *_toklen, n_parts, loop, tmp; + unsigned int toklen = *_toklen, n_parts, loop, tmp, paddedlen; /* there must be at least one name, and at least #names+1 length * words */ @@ -243,16 +243,16 @@ static int rxrpc_krb5_decode_principal(s toklen -= 4; if (tmp <= 0 || tmp > AFSTOKEN_STRING_MAX) return -EINVAL; - if (tmp > toklen) + paddedlen = (tmp + 3) & ~3; + if (paddedlen > toklen) return -EINVAL; princ->name_parts[loop] = kmalloc(tmp + 1, GFP_KERNEL); if (!princ->name_parts[loop]) return -ENOMEM; memcpy(princ->name_parts[loop], xdr, tmp); princ->name_parts[loop][tmp] = 0; - tmp = (tmp + 3) & ~3; - toklen -= tmp; - xdr += tmp >> 2; + toklen -= paddedlen; + xdr += paddedlen >> 2; } if (toklen < 4) @@ -261,16 +261,16 @@ static int rxrpc_krb5_decode_principal(s toklen -= 4; if (tmp <= 0 || tmp > AFSTOKEN_K5_REALM_MAX) return -EINVAL; - if (tmp > toklen) + paddedlen = (tmp + 3) & ~3; + if (paddedlen > toklen) return -EINVAL; princ->realm = kmalloc(tmp + 1, GFP_KERNEL); if (!princ->realm) return -ENOMEM; memcpy(princ->realm, xdr, tmp); princ->realm[tmp] = 0; - tmp = (tmp + 3) & ~3; - toklen -= tmp; - xdr += tmp >> 2; + toklen -= paddedlen; + xdr += paddedlen >> 2; _debug("%s/...@%s", princ->name_parts[0], princ->realm); @@ -289,7 +289,7 @@ static int rxrpc_krb5_decode_tagged_data unsigned int *_toklen) { const __be32 *xdr = *_xdr; - unsigned int toklen = *_toklen, len; + unsigned int toklen = *_toklen, len, paddedlen; /* there must be at least one tag and one length word */ if (toklen <= 8) @@ -303,15 +303,17 @@ static int rxrpc_krb5_decode_tagged_data toklen -= 8; if (len > max_data_size) return -EINVAL; + paddedlen = (len + 3) & ~3; + if (paddedlen > toklen) + return -EINVAL; td->data_len = len; if (len > 0) { td->data = kmemdup(xdr, len, GFP_KERNEL); if (!td->data) return -ENOMEM; - len = (len + 3) & ~3; - toklen -= len; - xdr += len >> 2; + toklen -= paddedlen; + xdr += paddedlen >> 2; } _debug("tag %x len %x", td->tag, td->data_len); @@ -383,7 +385,7 @@ static int rxrpc_krb5_decode_ticket(u8 * const __be32 **_xdr, unsigned int *_toklen) { const __be32 *xdr = *_xdr; - unsigned int toklen = *_toklen, len; + unsigned int toklen = *_toklen, len, paddedlen; /* there must be at least one length word */ if (toklen <= 4) @@ -395,6 +397,9 @@ static int rxrpc_krb5_decode_ticket(u8 * toklen -= 4; if (len > AFSTOKEN_K5_TIX_MAX) return -EINVAL; + paddedlen = (len + 3) & ~3; + if (paddedlen > toklen) + return -EINVAL; *_tktlen = len; _debug("ticket len %u", len); @@ -403,9 +408,8 @@ static int rxrpc_krb5_decode_ticket(u8 * *_ticket = kmemdup(xdr, len, GFP_KERNEL); if (!*_ticket) return -ENOMEM; - len = (len + 3) & ~3; - toklen -= len; - xdr += len >> 2; + toklen -= paddedlen; + xdr += paddedlen >> 2; } *_xdr = xdr; @@ -549,7 +553,7 @@ static int rxrpc_instantiate_xdr(struct { const __be32 *xdr = data, *token; const char *cp; - unsigned int len, tmp, loop, ntoken, toklen, sec_ix; + unsigned int len, paddedlen, loop, ntoken, toklen, sec_ix; int ret; _enter(",{%x,%x,%x,%x},%zu", @@ -574,22 +578,21 @@ static int rxrpc_instantiate_xdr(struct if (len < 1 || len > AFSTOKEN_CELL_MAX) goto not_xdr; datalen -= 4; - tmp = (len + 3) & ~3; - if (tmp > datalen) + paddedlen = (len + 3) & ~3; + if (paddedlen > datalen) goto not_xdr; cp = (const char *) xdr; for (loop = 0; loop < len; loop++) if (!isprint(cp[loop])) goto not_xdr; - if (len < tmp) - for (; loop < tmp; loop++) - if (cp[loop]) - goto not_xdr; + for (; loop < paddedlen; loop++) + if (cp[loop]) + goto not_xdr; _debug("cellname: [%u/%u] '%*.*s'", - len, tmp, len, len, (const char *) xdr); - datalen -= tmp; - xdr += tmp >> 2; + len, paddedlen, len, len, (const char *) xdr); + datalen -= paddedlen; + xdr += paddedlen >> 2; /* get the token count */ if (datalen < 12) @@ -610,10 +613,11 @@ static int rxrpc_instantiate_xdr(struct sec_ix = ntohl(*xdr); datalen -= 4; _debug("token: [%x/%zx] %x", toklen, datalen, sec_ix); - if (toklen < 20 || toklen > datalen) + paddedlen = (toklen + 3) & ~3; + if (toklen < 20 || toklen > datalen || paddedlen > datalen) goto not_xdr; - datalen -= (toklen + 3) & ~3; - xdr += (toklen + 3) >> 2; + datalen -= paddedlen; + xdr += paddedlen >> 2; } while (--loop > 0);