linux-kernel - [PATCH] afs: Use kfree_rcu() instead of casting kfree() to rcu_callback

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Date:   Thu, 12 Mar 2020 21:36:53 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     Jann Horn <jannh@...gle.com>, dhowells@...hat.com,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] afs: Use kfree_rcu() instead of casting kfree() to
 rcu_callback_t

From: Jann Horn <jannh@...gle.com>

afs_put_addrlist() casts kfree() to rcu_callback_t. Apart from being wrong
in theory, this might also blow up when people start enforcing function
types via compiler instrumentation, and it means the rcu_head has to be
first in struct afs_addr_list.

Use kfree_rcu() instead, it's simpler and more correct.

Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/addr_list.c |    2 +-
 fs/afs/internal.h  |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index df415c05939e..de1ae0bead3b 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -19,7 +19,7 @@
 void afs_put_addrlist(struct afs_addr_list *alist)
 {
 	if (alist && refcount_dec_and_test(&alist->usage))
-		call_rcu(&alist->rcu, (rcu_callback_t)kfree);
+		kfree_rcu(alist, rcu);
 }
 
 /*
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 1d81fc4c3058..35f951ac296f 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -81,7 +81,7 @@ enum afs_call_state {
  * List of server addresses.
  */
 struct afs_addr_list {
-	struct rcu_head		rcu;		/* Must be first */
+	struct rcu_head		rcu;
 	refcount_t		usage;
 	u32			version;	/* Version */
 	unsigned char		max_addrs;