diff --git a/ChangeLog b/ChangeLog
index 677e5e2107..7264a9d427 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2017-04-18  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #21267]
+	* sysdeps/unix/sysv/linux/bits/socket.h (IOCSIZE_MASK): Undefine
+	if defined by <asm/socket.h> and not previously defined.
+	(IOCSIZE_SHIFT): Likewise.
+	(IOC_IN): Likewise.
+	(IOC_INOUT): Likewise.
+	(IOC_OUT): Likewise.
+
 2017-04-18  H.J. Lu  <hongjiu.lu@intel.com>
 
 	[BZ #21396]
diff --git a/sysdeps/unix/sysv/linux/bits/socket.h b/sysdeps/unix/sysv/linux/bits/socket.h
index 0f1b7869d9..6d6d56e624 100644
--- a/sysdeps/unix/sysv/linux/bits/socket.h
+++ b/sysdeps/unix/sysv/linux/bits/socket.h
@@ -365,6 +365,21 @@ struct ucred
 #  define __SYS_SOCKET_H_undef_SIOCSPGRP
 # endif
 #endif
+#ifndef IOCSIZE_MASK
+# define __SYS_SOCKET_H_undef_IOCSIZE_MASK
+#endif
+#ifndef IOCSIZE_SHIFT
+# define __SYS_SOCKET_H_undef_IOCSIZE_SHIFT
+#endif
+#ifndef IOC_IN
+# define __SYS_SOCKET_H_undef_IOC_IN
+#endif
+#ifndef IOC_INOUT
+# define __SYS_SOCKET_H_undef_IOC_INOUT
+#endif
+#ifndef IOC_OUT
+# define __SYS_SOCKET_H_undef_IOC_OUT
+#endif
 
 /* Get socket manipulation related informations from kernel headers.  */
 #include <asm/socket.h>
@@ -399,6 +414,26 @@ struct ucred
 #  undef SIOCSPGRP
 # endif
 #endif
+#ifdef __SYS_SOCKET_H_undef_IOCSIZE_MASK
+# undef __SYS_SOCKET_H_undef_IOCSIZE_MASK
+# undef IOCSIZE_MASK
+#endif
+#ifdef __SYS_SOCKET_H_undef_IOCSIZE_SHIFT
+# undef __SYS_SOCKET_H_undef_IOCSIZE_SHIFT
+# undef IOCSIZE_SHIFT
+#endif
+#ifdef __SYS_SOCKET_H_undef_IOC_IN
+# undef __SYS_SOCKET_H_undef_IOC_IN
+# undef IOC_IN
+#endif
+#ifdef __SYS_SOCKET_H_undef_IOC_INOUT
+# undef __SYS_SOCKET_H_undef_IOC_INOUT
+# undef IOC_INOUT
+#endif
+#ifdef __SYS_SOCKET_H_undef_IOC_OUT
+# undef __SYS_SOCKET_H_undef_IOC_OUT
+# undef IOC_OUT
+#endif
 
 /* Structure used to manipulate the SO_LINGER option.  */
 struct linger