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

Al Viro
2024-11-02T05:08:29Z

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@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.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