sctp: Constify struct sctp_sched_ops

'struct sctp_sched_ops' is not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig, as an example:
Before:
======
text data bss dec hex filename
8019 568 0 8587 218b net/sctp/stream_sched_fc.o

After:
=====
text data bss dec hex filename
8275 312 0 8587 218b net/sctp/stream_sched_fc.o

Signed-off-by: Christophe JAILLET <[e-mail]>
Link: https://patch.msgid.link/dce03527eb[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/sctp/stream_sched.h

···
 
 void sctp_sched_dequeue_common(struct sctp_outq *q, struct sctp_chunk *ch);
 int sctp_sched_init_sid(struct sctp_stream *stream, __u16 sid, gfp_t gfp);
-struct sctp_sched_ops *sctp_sched_ops_from_stream(struct sctp_stream *stream);
+const struct sctp_sched_ops *sctp_sched_ops_from_stream(struct sctp_stream *stream);
 
 void sctp_sched_ops_register(enum sctp_sched_type sched,
-			     struct sctp_sched_ops *sched_ops);
+			     const struct sctp_sched_ops *sched_ops);
 void sctp_sched_ops_prio_init(void);
 void sctp_sched_ops_rr_init(void);
 void sctp_sched_ops_fc_init(void);

include/net/sctp/structs.h

···
 	struct list_head out_chunk_list;
 
 	/* Stream scheduler being used */
-	struct sctp_sched_ops *sched;
+	const struct sctp_sched_ops *sched;
 
 	unsigned int out_qlen;	/* Total length of queued data chunks. */
 

net/sctp/stream.c

···
 
 static void sctp_stream_free_ext(struct sctp_stream *stream, __u16 sid)
 {
-	struct sctp_sched_ops *sched;
+	const struct sctp_sched_ops *sched;
 
 	if (!SCTP_SO(stream, sid)->ext)
 		return;
···
 int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
 		     gfp_t gfp)
 {
-	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+	const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 	int i, ret = 0;
 
 	gfp |= __GFP_NOWARN;
···
 
 void sctp_stream_free(struct sctp_stream *stream)
 {
-	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+	const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 	int i;
 
 	sched->unsched_all(stream);
···
 
 void sctp_stream_update(struct sctp_stream *stream, struct sctp_stream *new)
 {
-	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+	const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 
 	sched->unsched_all(stream);
 	sctp_stream_outq_migrate(stream, new, new->outcnt);

net/sctp/stream_sched.c

···
 {
 }
 
-static struct sctp_sched_ops sctp_sched_fcfs = {
+static const struct sctp_sched_ops sctp_sched_fcfs = {
 	.set = sctp_sched_fcfs_set,
 	.get = sctp_sched_fcfs_get,
 	.init = sctp_sched_fcfs_init,
···
 
 /* API to other parts of the stack */
 
-static struct sctp_sched_ops *sctp_sched_ops[SCTP_SS_MAX + 1];
+static const struct sctp_sched_ops *sctp_sched_ops[SCTP_SS_MAX + 1];
 
 void sctp_sched_ops_register(enum sctp_sched_type sched,
-			     struct sctp_sched_ops *sched_ops)
+			     const struct sctp_sched_ops *sched_ops)
 {
 	sctp_sched_ops[sched] = sched_ops;
 }
···
 
 static void sctp_sched_free_sched(struct sctp_stream *stream)
 {
-	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+	const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 	struct sctp_stream_out_ext *soute;
 	int i;
 
···
 int sctp_sched_set_sched(struct sctp_association *asoc,
 			 enum sctp_sched_type sched)
 {
-	struct sctp_sched_ops *old = asoc->outqueue.sched;
+	const struct sctp_sched_ops *old = asoc->outqueue.sched;
 	struct sctp_datamsg *msg = NULL;
-	struct sctp_sched_ops *n;
+	const struct sctp_sched_ops *n;
 	struct sctp_chunk *ch;
 	int i, ret = 0;
 
···
 
 int sctp_sched_init_sid(struct sctp_stream *stream, __u16 sid, gfp_t gfp)
 {
-	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+	const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 	struct sctp_stream_out_ext *ext = SCTP_SO(stream, sid)->ext;
 
 	INIT_LIST_HEAD(&ext->outq);
 	return sched->init_sid(stream, sid, gfp);
 }
 
-struct sctp_sched_ops *sctp_sched_ops_from_stream(struct sctp_stream *stream)
+const struct sctp_sched_ops *sctp_sched_ops_from_stream(struct sctp_stream *stream)
 {
 	struct sctp_association *asoc;
 

net/sctp/stream_sched_fc.c

···
 		list_del_init(&soute->fc_list);
 }
 
-static struct sctp_sched_ops sctp_sched_fc = {
+static const struct sctp_sched_ops sctp_sched_fc = {
 	.set = sctp_sched_fc_set,
 	.get = sctp_sched_fc_get,
 	.init = sctp_sched_fc_init,
···
 	sctp_sched_ops_register(SCTP_SS_FC, &sctp_sched_fc);
 }
 
-static struct sctp_sched_ops sctp_sched_wfq = {
+static const struct sctp_sched_ops sctp_sched_wfq = {
 	.set = sctp_sched_wfq_set,
 	.get = sctp_sched_wfq_get,
 	.init = sctp_sched_fc_init,

net/sctp/stream_sched_prio.c

···
 			sctp_sched_prio_unsched(soute);
 }
 
-static struct sctp_sched_ops sctp_sched_prio = {
+static const struct sctp_sched_ops sctp_sched_prio = {
 	.set = sctp_sched_prio_set,
 	.get = sctp_sched_prio_get,
 	.init = sctp_sched_prio_init,

net/sctp/stream_sched_rr.c

···
 		sctp_sched_rr_unsched(stream, soute);
 }
 
-static struct sctp_sched_ops sctp_sched_rr = {
+static const struct sctp_sched_ops sctp_sched_rr = {
 	.set = sctp_sched_rr_set,
 	.get = sctp_sched_rr_get,
 	.init = sctp_sched_rr_init,