[CBR 7.9] CVE-2023-1281

include/linux/rcupdate.h

@@ -969,6 +969,24 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 #define rcu_assign_pointer(p, v) \
 	__rcu_assign_pointer((p), (v), __rcu)
 
+/**
+ * rcu_replace_pointer() - replace an RCU pointer, returning its old value
+ * @rcu_ptr: RCU pointer, whose old value is returned
+ * @ptr: regular pointer
+ * @c: the lockdep conditions under which the dereference will take place
+ *
+ * Perform a replacement, where @rcu_ptr is an RCU-annotated
+ * pointer and @c is the lockdep argument that is passed to the
+ * rcu_dereference_protected() call used to read that pointer.  The old
+ * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr.
+ */
+#define rcu_replace_pointer(rcu_ptr, ptr, c)				\
+({									\
+	typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c));	\
+	rcu_assign_pointer((rcu_ptr), (ptr));				\
+	__tmp;								\
+})
+
 /**
  * RCU_INIT_POINTER() - initialize an RCU protected pointer
  *

net/sched/cls_tcindex.c

@@ -10,6 +10,7 @@
 #include <linux/skbuff.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 #include <net/act_api.h>
 #include <net/netlink.h>
 #include <net/pkt_cls.h>
@@ -313,6 +314,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
 	struct tcindex_filter *f = NULL; /* make gcc behave */
 	int err, balloc = 0;
 	struct tcf_exts e;
+	bool update_h = false;
 
 	err = tcf_exts_init(&e, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
 	if (err < 0)
@@ -427,10 +429,13 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
 		}
 	}
 
-	if (cp->perfect)
+	if (cp->perfect) {
 		r = cp->perfect + handle;
-	else
-		r = tcindex_lookup(cp, handle) ? : &new_filter_result;
+	} else {
+		/* imperfect area is updated in-place using rcu */
+		update_h = !!tcindex_lookup(cp, handle);
+		r = &new_filter_result;
+	}
 
 	if (r == &new_filter_result) {
 		f = kzalloc(sizeof(*f), GFP_KERNEL);
@@ -464,7 +469,28 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
 
 	rcu_assign_pointer(tp->root, cp);
 
-	if (r == &new_filter_result) {
+	if (update_h) {
+		struct tcindex_filter __rcu **fp;
+		struct tcindex_filter *cf;
+
+		f->result.res = r->res;
+		tcf_exts_change(&f->result.exts, &r->exts);
+
+		/* imperfect area bucket */
+		fp = cp->h + (handle % cp->hash);
+
+		/* lookup the filter, guaranteed to exist */
+		for (cf = rcu_dereference_bh_rtnl(*fp); cf;
+		     fp = &cf->next, cf = rcu_dereference_bh_rtnl(*fp))
+			if (cf->key == (u16)handle)
+				break;
+
+		f->next = cf->next;
+
+		cf = rcu_replace_pointer(*fp, f, 1);
+		tcf_exts_get_net(&cf->result.exts);
+		tcf_queue_work(&cf->rwork, tcindex_destroy_fexts_work);
+	} else if (r == &new_filter_result) {
 		struct tcindex_filter *nfp;
 		struct tcindex_filter __rcu **fp;