Update Linux to v5.10.109

Sourced from [1]

[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz

Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/fs/nfs/sysfs.c b/fs/nfs/sysfs.c
index 4f3390b..8cb7075 100644
--- a/fs/nfs/sysfs.c
+++ b/fs/nfs/sysfs.c
@@ -79,7 +79,12 @@
 	struct nfs_netns_client *c = container_of(kobj,
 			struct nfs_netns_client,
 			kobject);
-	return scnprintf(buf, PAGE_SIZE, "%s\n", c->identifier);
+	ssize_t ret;
+
+	rcu_read_lock();
+	ret = scnprintf(buf, PAGE_SIZE, "%s\n", rcu_dereference(c->identifier));
+	rcu_read_unlock();
+	return ret;
 }
 
 /* Strip trailing '\n' */
@@ -107,7 +112,7 @@
 	p = kmemdup_nul(buf, len, GFP_KERNEL);
 	if (!p)
 		return -ENOMEM;
-	old = xchg(&c->identifier, p);
+	old = rcu_dereference_protected(xchg(&c->identifier, (char __rcu *)p), 1);
 	if (old) {
 		synchronize_rcu();
 		kfree(old);
@@ -121,8 +126,7 @@
 			struct nfs_netns_client,
 			kobject);
 
-	if (c->identifier)
-		kfree(c->identifier);
+	kfree(rcu_dereference_raw(c->identifier));
 	kfree(c);
 }