[PATCH resend] uapi/linux/keyctl.h: don't use C++ reserved keyword as a struct member name

From: Randy Dunlap <rdunlap@infradead.org>

Since this header is in "include/uapi/linux/", apparently people
want to use it in userspace programs -- even in C++ ones.
However, the header uses a C++ reserved keyword ("private"),
so change that to "dh_private" instead to allow the header file
to be used in C++ userspace.

Fixes https://bugzilla.kernel.org/show_bug.cgi?id=191051
Fixes: ddbb41148724 ("KEYS: Add KEYCTL_DH_COMPUTE command")

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: keyrings at vger.kernel.org
Cc: linux-security-module at vger.kernel.org
Cc: Mat Martineau <redacted>
Cc: stable at vger.kernel.org
---
 include/uapi/linux/keyctl.h |    2 +-
 security/keys/dh.c          |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- lnx-416.orig/include/uapi/linux/keyctl.h
+++ lnx-416/include/uapi/linux/keyctl.h

@@ -65,7 +65,7 @@
 
 /* keyctl structures */
 struct keyctl_dh_params {
-	__s32 private;
+	__s32 dh_private;
 	__s32 prime;
 	__s32 base;
 };
--- lnx-416.orig/security/keys/dh.c
+++ lnx-416/security/keys/dh.c

@@ -307,7 +307,7 @@ long __keyctl_dh_compute(struct keyctl_d
 	}
 	dh_inputs.g_size = dlen;
 
-	dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
+	dlen = dh_data_from_key(pcopy.dh_private, &dh_inputs.key);
 	if (dlen < 0) {
 		ret = dlen;
 		goto out2;

On Tue, Aug 28, 2018 at 04:34:04PM -0700, Randy Dunlap wrote:

Ick ick ick, why not just put the C "namespace" on all uapi files if you
are including them from c++ code?  I'm sure this isn't the only problem
that has this problem, right?

This is valid C, no need to start worrying about C++ reserved names.

thanks,

greg "'struct class' is your friend" k-h

On Tue, 28 Aug 2018 19:42:24 -0700 Greg KH [off-list ref] wrote:

quoted

--- lnx-416.orig/include/uapi/linux/keyctl.h
+++ lnx-416/include/uapi/linux/keyctl.h

@@ -65,7 +65,7 @@
 
 /* keyctl structures */
 struct keyctl_dh_params {
-	__s32 private;
+	__s32 dh_private;

Ick ick ick, why not just put the C "namespace" on all uapi files if you
are including them from c++ code?  I'm sure this isn't the only problem
that has this problem, right?

This is valid C, no need to start worrying about C++ reserved names.

We've done this before and it's a simple enough change in order to be
friendly toward others.

That being said, it's been like this for two years so presumably anyone
who is using this header from C++ is already `extern "C" { ...}' around
their #include.

I'm OK with the patch as-is, but if we run into this issue more often,
we might want to look at doing something kernel-wide.

I'm not sure what though. Adding

#ifdef __cplusplus
extern "C" {
#endif

...

#ifdef __cplusplus
}
#endif

into every uapi file might work.  Unpleasing.

On Tue, Aug 28, 2018 at 04:34:04PM -0700, Randy Dunlap wrote:

From: Randy Dunlap <rdunlap@infradead.org>

Since this header is in "include/uapi/linux/", apparently people
want to use it in userspace programs -- even in C++ ones.
However, the header uses a C++ reserved keyword ("private"),
so change that to "dh_private" instead to allow the header file
to be used in C++ userspace.

This change breaks all existing C programs that rely on <linux/keyctl.h>
uapi header in order to get struct keyctl_dh_params definition, however.

On Mon, 10 Sep 2018 00:00:18 +0200 Eugene Syromiatnikov [off-list ref] wrote:

On Tue, Aug 28, 2018 at 04:34:04PM -0700, Randy Dunlap wrote:

quoted

From: Randy Dunlap <rdunlap@infradead.org>

Since this header is in "include/uapi/linux/", apparently people
want to use it in userspace programs -- even in C++ ones.
However, the header uses a C++ reserved keyword ("private"),
so change that to "dh_private" instead to allow the header file
to be used in C++ userspace.

This change breaks all existing C programs that rely on <linux/keyctl.h>
uapi header in order to get struct keyctl_dh_params definition, however.

Are there such programs?  Do they reference the `private' field?

Andrew Morton [off-list ref] wrote:

Are there such programs?  Do they reference the `private' field?

They would use the keyutils.h header from keyutils package probably.  There
the field was named "priv" not "private".  The kernel's UAPI header should be
amended again to match that.

David