netdev - [PATCH v3 05/28] switch netlink_getsockbyfilp() to taking descriptor

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Message-ID: <20241102050827.2451599-5-viro@zeniv.linux.org.uk>
Date: Sat,  2 Nov 2024 05:08:03 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	cgroups@...r.kernel.org,
	kvm@...r.kernel.org,
	netdev@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: [PATCH v3 05/28] switch netlink_getsockbyfilp() to taking descriptor

the only call site (in do_mq_notify()) obtains the argument
from an immediately preceding fdget() and it is immediately
followed by fdput(); might as well just replace it with
a variant that would take a descriptor instead of struct file *
and have file lookups handled inside that function.

Reviewed-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 include/linux/netlink.h  | 2 +-
 ipc/mqueue.c             | 8 +-------
 net/netlink/af_netlink.c | 9 +++++++--
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index b332c2048c75..a48a30842d84 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -239,7 +239,7 @@ int netlink_register_notifier(struct notifier_block *nb);
 int netlink_unregister_notifier(struct notifier_block *nb);
 
 /* finegrained unicast helpers: */
-struct sock *netlink_getsockbyfilp(struct file *filp);
+struct sock *netlink_getsockbyfd(int fd);
 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 		      long *timeo, struct sock *ssk);
 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 34fa0bd8bb11..fd05e3d4f7b6 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -1355,13 +1355,7 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 			skb_put(nc, NOTIFY_COOKIE_LEN);
 			/* and attach it to the socket */
 retry:
-			f = fdget(notification->sigev_signo);
-			if (!fd_file(f)) {
-				ret = -EBADF;
-				goto out;
-			}
-			sock = netlink_getsockbyfilp(fd_file(f));
-			fdput(f);
+			sock = netlink_getsockbyfd(notification->sigev_signo);
 			if (IS_ERR(sock)) {
 				ret = PTR_ERR(sock);
 				goto free_skb;
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 0b7a89db3ab7..42451ac355d0 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1180,11 +1180,16 @@ static struct sock *netlink_getsockbyportid(struct sock *ssk, u32 portid)
 	return sock;
 }
 
-struct sock *netlink_getsockbyfilp(struct file *filp)
+struct sock *netlink_getsockbyfd(int fd)
 {
-	struct inode *inode = file_inode(filp);
+	CLASS(fd, f)(fd);
+	struct inode *inode;
 	struct sock *sock;
 
+	if (fd_empty(f))
+		return ERR_PTR(-EBADF);
+
+	inode = file_inode(fd_file(f));
 	if (!S_ISSOCK(inode->i_mode))
 		return ERR_PTR(-ENOTSOCK);
 
-- 
2.39.5