Merge tag 'nfsd-6.2-5' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux

Pull nfsd fix from Chuck Lever:

 - Nail another UAF in NFSD's filecache

* tag 'nfsd-6.2-5' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux:
  nfsd: don't free files unconditionally in __nfsd_file_cache_purge

Author: torvalds

fs/nfsd/filecache.c

@@ -661,6 +661,39 @@ static struct shrinker	nfsd_file_shrinker = {
 	.seeks = 1,
 };
 
+/**
+ * nfsd_file_cond_queue - conditionally unhash and queue a nfsd_file
+ * @nf: nfsd_file to attempt to queue
+ * @dispose: private list to queue successfully-put objects
+ *
+ * Unhash an nfsd_file, try to get a reference to it, and then put that
+ * reference. If it's the last reference, queue it to the dispose list.
+ */
+static void
+nfsd_file_cond_queue(struct nfsd_file *nf, struct list_head *dispose)
+	__must_hold(RCU)
+{
+	int decrement = 1;
+
+	/* If we raced with someone else unhashing, ignore it */
+	if (!nfsd_file_unhash(nf))
+		return;
+
+	/* If we can't get a reference, ignore it */
+	if (!nfsd_file_get(nf))
+		return;
+
+	/* Extra decrement if we remove from the LRU */
+	if (nfsd_file_lru_remove(nf))
+		++decrement;
+
+	/* If refcount goes to 0, then put on the dispose list */
+	if (refcount_sub_and_test(decrement, &nf->nf_ref)) {
+		list_add(&nf->nf_lru, dispose);
+		trace_nfsd_file_closing(nf);
+	}
+}
+
 /**
  * nfsd_file_queue_for_close: try to close out any open nfsd_files for an inode
  * @inode:   inode on which to close out nfsd_files
@@ -688,30 +721,11 @@ nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 
 	rcu_read_lock();
 	do {
-		int decrement = 1;
-
 		nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key,
 				       nfsd_file_rhash_params);
 		if (!nf)
 			break;
-
-		/* If we raced with someone else unhashing, ignore it */
-		if (!nfsd_file_unhash(nf))
-			continue;
-
-		/* If we can't get a reference, ignore it */
-		if (!nfsd_file_get(nf))
-			continue;
-
-		/* Extra decrement if we remove from the LRU */
-		if (nfsd_file_lru_remove(nf))
-			++decrement;
-
-		/* If refcount goes to 0, then put on the dispose list */
-		if (refcount_sub_and_test(decrement, &nf->nf_ref)) {
-			list_add(&nf->nf_lru, dispose);
-			trace_nfsd_file_closing(nf);
-		}
+		nfsd_file_cond_queue(nf, dispose);
 	} while (1);
 	rcu_read_unlock();
 }
@@ -928,11 +942,8 @@ __nfsd_file_cache_purge(struct net *net)
 
 		nf = rhashtable_walk_next(&iter);
 		while (!IS_ERR_OR_NULL(nf)) {
-			if (!net || nf->nf_net == net) {
-				nfsd_file_unhash(nf);
-				nfsd_file_lru_remove(nf);
-				list_add(&nf->nf_lru, &dispose);
-			}
+			if (!net || nf->nf_net == net)
+				nfsd_file_cond_queue(nf, &dispose);
 			nf = rhashtable_walk_next(&iter);
 		}