SUNRPC: introduce cache_check_rcu to help check in rcu context

JIRA: https://issues.redhat.com/browse/RHEL-80508
CVE: CVE-2024-53216

commit 2f55dbe
Author: Yang Erkun <yangerkun@huawei.com>
Date:   Wed Dec 25 14:59:05 2024 +0800

    SUNRPC: introduce cache_check_rcu to help check in rcu context

    This is a prepare patch to add cache_check_rcu, will use it with follow
    patch.

    Suggested-by: NeilBrown <neilb@suse.de>
    Signed-off-by: Yang Erkun <yangerkun@huawei.com>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>

Author: Olga Kornievskaia

include/linux/sunrpc/cache.h

@@ -222,6 +222,8 @@ static inline bool cache_is_expired(struct cache_detail *detail, struct cache_he
 	return detail->flush_time >= h->last_refresh;
 }
 
+extern int cache_check_rcu(struct cache_detail *detail,
+		       struct cache_head *h, struct cache_req *rqstp);
 extern int cache_check(struct cache_detail *detail,
 		       struct cache_head *h, struct cache_req *rqstp);
 extern void cache_flush(void);

net/sunrpc/cache.c

@@ -281,21 +281,7 @@ static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h
 	return rv;
 }
 
-/*
- * This is the generic cache management routine for all
- * the authentication caches.
- * It checks the currency of a cache item and will (later)
- * initiate an upcall to fill it if needed.
- *
- *
- * Returns 0 if the cache_head can be used, or cache_puts it and returns
- * -EAGAIN if upcall is pending and request has been queued
- * -ETIMEDOUT if upcall failed or request could not be queue or
- *           upcall completed but item is still invalid (implying that
- *           the cache item has been replaced with a newer one).
- * -ENOENT if cache entry was negative
- */
-int cache_check(struct cache_detail *detail,
+int cache_check_rcu(struct cache_detail *detail,
 		    struct cache_head *h, struct cache_req *rqstp)
 {
 	int rv;
@@ -336,6 +322,31 @@ int cache_check(struct cache_detail *detail,
 				rv = -ETIMEDOUT;
 		}
 	}
+
+	return rv;
+}
+EXPORT_SYMBOL_GPL(cache_check_rcu);
+
+/*
+ * This is the generic cache management routine for all
+ * the authentication caches.
+ * It checks the currency of a cache item and will (later)
+ * initiate an upcall to fill it if needed.
+ *
+ *
+ * Returns 0 if the cache_head can be used, or cache_puts it and returns
+ * -EAGAIN if upcall is pending and request has been queued
+ * -ETIMEDOUT if upcall failed or request could not be queue or
+ *           upcall completed but item is still invalid (implying that
+ *           the cache item has been replaced with a newer one).
+ * -ENOENT if cache entry was negative
+ */
+int cache_check(struct cache_detail *detail,
+		struct cache_head *h, struct cache_req *rqstp)
+{
+	int rv;
+
+	rv = cache_check_rcu(detail, h, rqstp);
 	if (rv)
 		cache_put(h, detail);
 	return rv;