isdn_ppp: Add checks for allocation failure in isdn_ppp_open()

commit 0baa57d8 upstream.

Compile-tested only.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Reference: CVE-2015-7799
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/isdn/i4l/isdn_ppp.c

@@ -301,6 +301,8 @@ isdn_ppp_open(int min, struct file *file)
 	is->compflags = 0;
 
 	is->reset = isdn_ppp_ccp_reset_alloc(is);
+	if (!is->reset)
+		return -ENOMEM;
 
 	is->lp = NULL;
 	is->mp_seqno = 0;       /* MP sequence number */
@@ -320,6 +322,10 @@ isdn_ppp_open(int min, struct file *file)
 	 * VJ header compression init
 	 */
 	is->slcomp = slhc_init(16, 16);	/* not necessary for 2. link in bundle */
+	if (!is->slcomp) {
+		isdn_ppp_ccp_reset_free(is);
+		return -ENOMEM;
+	}
 #endif
 #ifdef CONFIG_IPPP_FILTER
 	is->pass_filter = NULL;