libexport: Fix IP address check in check_netgroup()

Neil Brown reports that recent changes to replace
gethostby{addr,name}(3) with get{addr,info}name(3) may have
inadvertently broken netgroup support.

There used to be a gethostbyaddr(3) call in the third paragraph in
check_netgroup().  The reason for that gethostbyaddr(3) call was that
the first innetgr(3) call has already confirmed that hname is not a
member of the netgroup.  We also need to confirm that, if hname
happens to be an IP address, the hostname bound to that IP address is
not a member of the netgroup, either.

Fix this by restoring appropriate address to hostname mapping of hname
before retrying the innetgr(3) call.

See http://marc.info/?l=linux-nfs&m=128084830214653&w=2 .

Introduced by commit 0509d3428f523776ddd9d6e9fa318587d3ec7d84.

Reviewed-by: Neil Brown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/support/export/client.c b/support/export/client.c
index b1a3a09d680d32b2f5e70aaf3c847bf4b1b0b18f..21001ce282dd85ecbe038fa0d53b98ac5e55a043 100644 (file)
--- a/support/export/client.c
+++ b/support/export/client.c
@@ -490,14 +490,19 @@ static int
 check_netgroup(const nfs_client *clp, const struct addrinfo *ai)
 {
        const char *netgroup = clp->m_hostname + 1;
-       const char *hname = ai->ai_canonname;
        struct addrinfo *tmp = NULL;
        struct hostent *hp;
+       char *dot, *hname;
        int i, match;
-       char *dot;
 
        match = 0;
 
+       hname = strdup(ai->ai_canonname);
+       if (hname == NULL) {
+               xlog(D_GENERAL, "%s: no memory for strdup", __func__);
+               goto out;
+       }
+
        /* First, try to match the hostname without
         * splitting off the domain */
        if (innetgr(netgroup, hname, NULL, NULL)) {
@@ -516,13 +521,21 @@ check_netgroup(const nfs_client *clp, const struct addrinfo *ai)
                        }
        }
 
-       /* If hname is ip address convert to FQDN */
+       /* If hname happens to be an IP address, convert it
+        * to a the canonical DNS name bound to this address. */
        tmp = host_pton(hname);
        if (tmp != NULL) {
+               char *cname = host_canonname(tmp->ai_addr);
                freeaddrinfo(tmp);
-               if (innetgr(netgroup, hname, NULL, NULL)) {
-                       match = 1;
-                       goto out;
+
+               /* The resulting FQDN may be in our netgroup. */
+               if (cname != NULL) {
+                       free(hname);
+                       hname = cname;
+                       if (innetgr(netgroup, hname, NULL, NULL)) {
+                               match = 1;
+                               goto out;
+                       }
                }
        }
 
@@ -533,9 +546,9 @@ check_netgroup(const nfs_client *clp, const struct addrinfo *ai)
 
        *dot = '\0';
        match = innetgr(netgroup, hname, NULL, NULL);
-       *dot = '.';
 
 out:
+       free(hname);
        return match;
 }
 #else  /* !HAVE_INNETGR */