sctp: Clean up type-punning in sctp_cmd_t union

Lots of points in the sctp_cmd_interpreter function treat the sctp_cmd_t arg as
a void pointer, even though they are written as various other types.  Theres no
need for this as doing so just leads to possible type-punning issues that could
cause crashes, and if we remain type-consistent we can actually just remove the
void * member of the union entirely.

Change Notes:

v2)
	* Dropped chunk that modified SCTP_NULL to create a marker pattern
	 should anyone try to use a SCTP_NULL() assigned sctp_arg_t, Assigning
	 to .zero provides the same effect and should be faster, per Vlad Y.

v3)
	* Reverted part of V2, opting to use memset instead of .zero, so that
	 the entire union is initalized thus avoiding the i164 speculative load
	 problems previously encountered, per Dave M..  Also rewrote
	 SCTP_[NO]FORCE so as to use common infrastructure a little more

Signed-off-by: Neil Horman <nhorman@tuxdriver.com
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: linux-sctp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 16 deletions

diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
index 712b3bebeda7..35247271e557 100644
--- a/include/net/sctp/command.h
+++ b/include/net/sctp/command.h
@@ -130,8 +130,6 @@ typedef union {
 	__be16 err;
 	sctp_state_t state;
 	sctp_event_timeout_t to;
-	unsigned long zero;
-	void *ptr;
 	struct sctp_chunk *chunk;
 	struct sctp_association *asoc;
 	struct sctp_transport *transport;
@@ -154,23 +152,15 @@ typedef union {
  * which takes an __s32 and returns a sctp_arg_t containing the
  * __s32.  So, after foo = SCTP_I32(arg), foo.i32 == arg.
  */
-static inline sctp_arg_t SCTP_NULL(void)
-{
-	sctp_arg_t retval; retval.ptr = NULL; return retval;
-}
-static inline sctp_arg_t SCTP_NOFORCE(void)
-{
-	sctp_arg_t retval = {.zero = 0UL}; retval.i32 = 0; return retval;
-}
-static inline sctp_arg_t SCTP_FORCE(void)
-{
-	sctp_arg_t retval = {.zero = 0UL}; retval.i32 = 1; return retval;
-}
 
 #define SCTP_ARG_CONSTRUCTOR(name, type, elt) \
 static inline sctp_arg_t	\
 SCTP_## name (type arg)		\
-{ sctp_arg_t retval = {.zero = 0UL}; retval.elt = arg; return retval; }
+{ sctp_arg_t retval;\
+  memset(&retval, 0, sizeof(sctp_arg_t));\
+  retval.elt = arg;\
+  return retval;\
+}
 
 SCTP_ARG_CONSTRUCTOR(I32,	__s32, i32)
 SCTP_ARG_CONSTRUCTOR(U32,	__u32, u32)
@@ -181,7 +171,6 @@ SCTP_ARG_CONSTRUCTOR(ERROR,     int, error)
 SCTP_ARG_CONSTRUCTOR(PERR,      __be16, err)	/* protocol error */
 SCTP_ARG_CONSTRUCTOR(STATE,	sctp_state_t, state)
 SCTP_ARG_CONSTRUCTOR(TO,	sctp_event_timeout_t, to)
-SCTP_ARG_CONSTRUCTOR(PTR,	void *, ptr)
 SCTP_ARG_CONSTRUCTOR(CHUNK,	struct sctp_chunk *, chunk)
 SCTP_ARG_CONSTRUCTOR(ASOC,	struct sctp_association *, asoc)
 SCTP_ARG_CONSTRUCTOR(TRANSPORT,	struct sctp_transport *, transport)
@@ -192,6 +181,23 @@ SCTP_ARG_CONSTRUCTOR(PACKET,	struct sctp_packet *, packet)
 SCTP_ARG_CONSTRUCTOR(SACKH,	sctp_sackhdr_t *, sackh)
 SCTP_ARG_CONSTRUCTOR(DATAMSG,	struct sctp_datamsg *, msg)
 
+static inline sctp_arg_t SCTP_FORCE(void)
+{
+	return SCTP_I32(1);
+}
+
+static inline sctp_arg_t SCTP_NOFORCE(void)
+{
+	return SCTP_I32(0);
+}
+
+static inline sctp_arg_t SCTP_NULL(void)
+{
+	sctp_arg_t retval;
+	memset(&retval, 0, sizeof(sctp_arg_t));
+	return retval;
+}
+
 typedef struct {
 	sctp_arg_t obj;
 	sctp_verb_t verb;