dlm: validate data in dlm_recover_directory()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/dir.c

@@ -220,6 +220,7 @@ int dlm_recover_directory(struct dlm_ls *ls)
 		last_len = 0;
 
 		for (;;) {
+			int left;
 			error = dlm_recovery_stopped(ls);
 			if (error)
 				goto out_free;
@@ -236,11 +237,20 @@ int dlm_recover_directory(struct dlm_ls *ls)
 			 */
 
 			b = ls->ls_recover_buf->rc_buf;
+			left = ls->ls_recover_buf->rc_header.h_length;
+			left -= sizeof(struct dlm_rcom);
 
 			for (;;) {
-				memcpy(&namelen, b, sizeof(uint16_t));
-				namelen = be16_to_cpu(namelen);
-				b += sizeof(uint16_t);
+				__be16 v;
+
+				error = -EINVAL;
+				if (left < sizeof(__be16))
+					goto out_free;
+
+				memcpy(&v, b, sizeof(__be16));
+				namelen = be16_to_cpu(v);
+				b += sizeof(__be16);
+				left -= sizeof(__be16);
 
 				/* namelen of 0xFFFFF marks end of names for
 				   this node; namelen of 0 marks end of the
@@ -251,6 +261,12 @@ int dlm_recover_directory(struct dlm_ls *ls)
 				if (!namelen)
 					break;
 
+				if (namelen > left)
+					goto out_free;
+
+				if (namelen > DLM_RESNAME_MAXLEN)
+					goto out_free;
+
 				error = -ENOMEM;
 				de = get_free_de(ls, namelen);
 				if (!de)
@@ -262,6 +278,7 @@ int dlm_recover_directory(struct dlm_ls *ls)
 				memcpy(de->name, b, namelen);
 				memcpy(last_name, b, namelen);
 				b += namelen;
+				left -= namelen;
 
 				add_entry_to_hash(ls, de);
 				count++;