Patch "uapi/if_ether.h: move __UAPI_DEF_ETHHDR libc define" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

uapi/if_ether.h: move __UAPI_DEF_ETHHDR libc define

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
uapi-if_ether.h-move-__uapi_def_ethhdr-libc-define.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Hauke Mehrtens <[email protected]>
Date: Mon, 12 Feb 2018 23:59:51 +0100
Subject: uapi/if_ether.h: move __UAPI_DEF_ETHHDR libc define

From: Hauke Mehrtens <[email protected]>

commit da360299b6734135a5f66d7db458dcc7801c826a upstream.

This fixes a compile problem of some user space applications by not including linux/libc-compat.h in uapi/if_ether.h.

linux/libc-compat.h checks which "features" the header files, included from the libc, provide to make the Linux kernel uapi header files only provide no conflicting structures and enums. If a user application mixes kernel headers and libc headers it could happen that linux/libc-compat.h gets included too early where not all other libc headers are included yet. Then the linux/libc-compat.h would not prevent all the redefinitions and we run into compile problems.
This patch removes the include of linux/libc-compat.h from uapi/if_ether.h to fix the recently introduced case, but not all as this is more or less impossible.

It is no problem to do the check directly in the if_ether.h file and not in libc-compat.h as this does not need any fancy glibc header detection as glibc never provided struct ethhdr and should define __UAPI_DEF_ETHHDR by them self when they will provide this.

The following test program did not compile correctly any more:

#include <linux/if_ether.h>
#include <netinet/in.h>
#include <linux/in.h>

int main(void)

{
	return 0;
}

---
 include/uapi/linux/if_ether.h    |    6 +++++-
 include/uapi/linux/libc-compat.h |    6 ------
 2 files changed, 5 insertions(+), 7 deletions(-)

@@ -23,7 +23,6 @@
 #define _UAPI_LINUX_IF_ETHER_H
 
 #include <linux/types.h>
-#include <linux/libc-compat.h>
 
 /*
  *	IEEE 802.3 Ethernet magic constants.  The frame sizes omit the preamble

@@ -150,6 +149,11 @@
  *	This is an Ethernet frame header.
  */
 
+/* allow libcs like musl to deactivate this, glibc does not implement this. */
+#ifndef __UAPI_DEF_ETHHDR
+#define __UAPI_DEF_ETHHDR		1
+#endif
+
 #if __UAPI_DEF_ETHHDR
 struct ethhdr {
 	unsigned char	h_dest[ETH_ALEN];	/* destination eth addr	*/

@@ -264,10 +264,4 @@
 
 #endif /* __GLIBC__ */
 
-/* Definitions for if_ether.h */
-/* allow libcs like musl to deactivate this, glibc does not implement this. */
-#ifndef __UAPI_DEF_ETHHDR
-#define __UAPI_DEF_ETHHDR		1
-#endif
-
 #endif /* _UAPI_LIBC_COMPAT_H */

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/uapi-if_ether.h-move-__uapi_def_ethhdr-libc-define.patch