--- /dev/null
+From 5f2f97656ada8d811d3c1bef503ced266fcd53a0 Mon Sep 17 00:00:00 2001
+From: David Howells <dhowells@redhat.com>
+Date: Thu, 15 Jun 2017 00:12:24 +0100
+Subject: rxrpc: Fix several cases where a padded len isn't checked in ticket decode
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: David Howells <dhowells@redhat.com>
+
+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 <shilei-c@360.cn>
+Signed-off-by: David Howells <dhowells@redhat.com>
+Reviewed-by: Marc Dionne <marc.c.dionne@auristor.com>
+Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ 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
+@@ -215,7 +215,7 @@ 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 */
+@@ -245,16 +245,16 @@ 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)
+@@ -263,16 +263,16 @@ 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);
+
+@@ -291,7 +291,7 @@ 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)
+@@ -305,15 +305,17 @@ 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);
+@@ -385,7 +387,7 @@ 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)
+@@ -397,6 +399,9 @@ 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);
+@@ -405,9 +410,8 @@ 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;
+@@ -550,7 +554,7 @@ static int rxrpc_preparse_xdr(struct key
+ {
+ const __be32 *xdr = prep->data, *token;
+ const char *cp;
+- unsigned int len, tmp, loop, ntoken, toklen, sec_ix;
++ unsigned int len, paddedlen, loop, ntoken, toklen, sec_ix;
+ size_t datalen = prep->datalen;
+ int ret;
+
+@@ -576,22 +580,21 @@ static int rxrpc_preparse_xdr(struct key
+ 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)
+@@ -612,10 +615,11 @@ static int rxrpc_preparse_xdr(struct key
+ 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);
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
