[PATCH v4] sgi-xp: Use designated initializers

[PATCH v4] sgi-xp: Use designated initializers

[Kees Cook]

Prepare to mark sensitive kernel structures for randomization by making
sure they're using designated initializers. In this case, no initializers
are needed (they can be NULL initialized and callers adjusted to check
for NULL, which is more efficient than an indirect call).

Cc: Robin Holt <robinmholt@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Brown paper bag release: forgot to actually commit a hunk...
---
 drivers/misc/sgi-xp/xp.h      | 12 +++++++++++-
 drivers/misc/sgi-xp/xp_main.c | 36 +++++++-----------------------------
 2 files changed, 18 insertions(+), 30 deletions(-)

diff --git a/drivers/misc/sgi-xp/xp.h b/drivers/misc/sgi-xp/xp.h
index c862cd4583cc..b8069eec18cb 100644
--- a/drivers/misc/sgi-xp/xp.h
+++ b/drivers/misc/sgi-xp/xp.h
@@ -309,6 +309,9 @@ static inline enum xp_retval
 xpc_send(short partid, int ch_number, u32 flags, void *payload,
 	 u16 payload_size)
 {
+	if (!xpc_interface.send)
+		return xpNotLoaded;
+
 	return xpc_interface.send(partid, ch_number, flags, payload,
 				  payload_size);
 }
@@ -317,6 +320,9 @@ static inline enum xp_retval
 xpc_send_notify(short partid, int ch_number, u32 flags, void *payload,
 		u16 payload_size, xpc_notify_func func, void *key)
 {
+	if (!xpc_interface.send_notify)
+		return xpNotLoaded;
+
 	return xpc_interface.send_notify(partid, ch_number, flags, payload,
 					 payload_size, func, key);
 }
@@ -324,12 +330,16 @@ xpc_send_notify(short partid, int ch_number, u32 flags, void *payload,
 static inline void
 xpc_received(short partid, int ch_number, void *payload)
 {
-	return xpc_interface.received(partid, ch_number, payload);
+	if (xpc_interface.received)
+		xpc_interface.received(partid, ch_number, payload);
 }
 
 static inline enum xp_retval
 xpc_partid_to_nasids(short partid, void *nasids)
 {
+	if (!xpc_interface.partid_to_nasids)
+		return xpNotLoaded;
+
 	return xpc_interface.partid_to_nasids(partid, nasids);
 }
 
diff --git a/drivers/misc/sgi-xp/xp_main.c b/drivers/misc/sgi-xp/xp_main.c
index 01be66d02ca8..6d7f557fd1c1 100644
--- a/drivers/misc/sgi-xp/xp_main.c
+++ b/drivers/misc/sgi-xp/xp_main.c
@@ -69,23 +69,9 @@ struct xpc_registration xpc_registrations[XPC_MAX_NCHANNELS];
 EXPORT_SYMBOL_GPL(xpc_registrations);
 
 /*
- * Initialize the XPC interface to indicate that XPC isn't loaded.
+ * Initialize the XPC interface to NULL to indicate that XPC isn't loaded.
  */
-static enum xp_retval
-xpc_notloaded(void)
-{
-	return xpNotLoaded;
-}
-
-struct xpc_interface xpc_interface = {
-	(void (*)(int))xpc_notloaded,
-	(void (*)(int))xpc_notloaded,
-	(enum xp_retval(*)(short, int, u32, void *, u16))xpc_notloaded,
-	(enum xp_retval(*)(short, int, u32, void *, u16, xpc_notify_func,
-			   void *))xpc_notloaded,
-	(void (*)(short, int, void *))xpc_notloaded,
-	(enum xp_retval(*)(short, void *))xpc_notloaded
-};
+struct xpc_interface xpc_interface = { };
 EXPORT_SYMBOL_GPL(xpc_interface);
 
 /*
@@ -115,17 +101,7 @@ EXPORT_SYMBOL_GPL(xpc_set_interface);
 void
 xpc_clear_interface(void)
 {
-	xpc_interface.connect = (void (*)(int))xpc_notloaded;
-	xpc_interface.disconnect = (void (*)(int))xpc_notloaded;
-	xpc_interface.send = (enum xp_retval(*)(short, int, u32, void *, u16))
-	    xpc_notloaded;
-	xpc_interface.send_notify = (enum xp_retval(*)(short, int, u32, void *,
-						       u16, xpc_notify_func,
-						       void *))xpc_notloaded;
-	xpc_interface.received = (void (*)(short, int, void *))
-	    xpc_notloaded;
-	xpc_interface.partid_to_nasids = (enum xp_retval(*)(short, void *))
-	    xpc_notloaded;
+	memset(&xpc_interface, 0, sizeof(xpc_interface));
 }
 EXPORT_SYMBOL_GPL(xpc_clear_interface);
 
@@ -188,7 +164,8 @@ xpc_connect(int ch_number, xpc_channel_func func, void *key, u16 payload_size,
 
 	mutex_unlock(&registration->mutex);
 
-	xpc_interface.connect(ch_number);
+	if (xpc_interface.connect)
+		xpc_interface.connect(ch_number);
 
 	return xpSuccess;
 }
@@ -237,7 +214,8 @@ xpc_disconnect(int ch_number)
 	registration->assigned_limit = 0;
 	registration->idle_limit = 0;
 
-	xpc_interface.disconnect(ch_number);
+	if (xpc_interface.disconnect)
+		xpc_interface.disconnect(ch_number);
 
 	mutex_unlock(&registration->mutex);
 
-- 
2.7.4


-- 
Kees Cook
Pixel Security

Re: [PATCH v4] sgi-xp: Use designated initializers

[Christoph Hellwig]

On Sat, May 27, 2017 at 05:39:14PM -0700, Kees Cook wrote:
> Prepare to mark sensitive kernel structures for randomization by making
> sure they're using designated initializers. In this case, no initializers
> are needed (they can be NULL initialized and callers adjusted to check
> for NULL, which is more efficient than an indirect call).

I'd say this looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Until I noticed all this is unused, so we should just remove it
entirely.  I now remember the weird SGI excuse, but given that they
haven't managed to get their code upstream in more than 10 years there
is no valid reason at all to keep this around.