[PATCH 1/4] NFS: validate pNFS data server port octets

[Prabhakar Pujeri <prabhakar.pujeri@dell.com>]

nfs4_decode_mp_ds_addr() parses the two decimal port octets in a
server-provided universal address with an unchecked sscanf(). A missing
or non-numeric field leaves part of the temporary array uninitialized,
while values outside the octet range are silently folded into the
resulting port.

Split the two port fields at their delimiters and parse each with
kstrtou8(). This rejects missing fields, trailing garbage, integer
overflow, and values outside 0 through 255 before constructing the data
server socket address.

Fixes: 6b7f3cf96364 ("nfs41: pull decode_ds_addr from file layout to generic pnfs")
Cc: stable@vger.kernel.org
Signed-off-by: Prabhakar Pujeri <prabhakar.pujeri@dell.com>
---
 fs/nfs/pnfs_nfs.c | 47 ++++++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
index b539e1a44d26..0c8c50eab4ad 100644
--- a/fs/nfs/pnfs_nfs.c
+++ b/fs/nfs/pnfs_nfs.c
@@ -8,6 +8,7 @@
  * Tom Haynes <loghyr@primarydata.com>
  */
 
+#include <linux/ctype.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
 #include <linux/sunrpc/addr.h>
@@ -1059,6 +1060,19 @@ int nfs4_pnfs_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds,
 }
 EXPORT_SYMBOL_GPL(nfs4_pnfs_ds_connect);
 
+static int
+nfs4_parse_port_octet(const char *str, u8 *port)
+{
+	const char *p;
+
+	if (!*str)
+		return -EINVAL;
+	for (p = str; *p; p++)
+		if (!isdigit(*p))
+			return -EINVAL;
+	return kstrtou8(str, 10, port);
+}
+
 /*
  * Currently only supports ipv4, ipv6 and one multi-path address.
  */
@@ -1066,10 +1080,10 @@ struct nfs4_pnfs_ds_addr *
 nfs4_decode_mp_ds_addr(struct net *net, struct xdr_stream *xdr, gfp_t gfp_flags)
 {
 	struct nfs4_pnfs_ds_addr *da = NULL;
-	char *buf, *portstr;
+	char *buf, *portsep;
 	__be16 port;
 	ssize_t nlen, rlen;
-	int tmp[2];
+	u8 porthi, portlo;
 	char *netid;
 	size_t len;
 	char *startsep = "";
@@ -1089,37 +1103,33 @@ nfs4_decode_mp_ds_addr(struct net *net, struct xdr_stream *xdr, gfp_t gfp_flags)
 	if (unlikely(rlen <= 0))
 		goto out_free_netid;
 
-	/* replace port '.' with '-' */
-	portstr = strrchr(buf, '.');
-	if (!portstr) {
-		dprintk("%s: Failed finding expected dot in port\n",
-			__func__);
+	/* Parse the low port octet and remove it from the address string. */
+	portsep = strrchr(buf, '.');
+	if (!portsep || nfs4_parse_port_octet(portsep + 1, &portlo)) {
+		dprintk("%s: Failed parsing low port octet\n", __func__);
 		goto out_free_buf;
 	}
-	*portstr = '-';
+	*portsep = '\0';
 
-	/* find '.' between address and port */
-	portstr = strrchr(buf, '.');
-	if (!portstr) {
-		dprintk("%s: Failed finding expected dot between address and "
-			"port\n", __func__);
+	/* Parse the high port octet and terminate the address string. */
+	portsep = strrchr(buf, '.');
+	if (!portsep || nfs4_parse_port_octet(portsep + 1, &porthi)) {
+		dprintk("%s: Failed parsing high port octet\n", __func__);
 		goto out_free_buf;
 	}
-	*portstr = '\0';
+	*portsep = '\0';
 
 	da = nfs4_pnfs_ds_addr_alloc(gfp_flags);
 	if (unlikely(!da))
 		goto out_free_buf;
 
-	if (!rpc_pton(net, buf, portstr-buf, (struct sockaddr *)&da->da_addr,
+	if (!rpc_pton(net, buf, portsep - buf, (struct sockaddr *)&da->da_addr,
 		      sizeof(da->da_addr))) {
 		dprintk("%s: error parsing address %s\n", __func__, buf);
 		goto out_free_da;
 	}
 
-	portstr++;
-	sscanf(portstr, "%d-%d", &tmp[0], &tmp[1]);
-	port = htons((tmp[0] << 8) | (tmp[1]));
+	port = htons((porthi << 8) | portlo);
 
 	switch (da->da_addr.ss_family) {
 	case AF_INET:
@@ -1226,4 +1236,3 @@ pnfs_nfs_generic_sync(struct inode *inode, bool datasync)
 	return pnfs_layoutcommit_inode(inode, true);
 }
 EXPORT_SYMBOL_GPL(pnfs_nfs_generic_sync);
-
-- 
2.54.0