Re: [PATCH v2 net-next 2/4] af_unix: Return struct unix_sock from unix_get_socket().

[Paolo Abeni <pabeni@redhat.com>]

On Wed, 2023-11-22 at 17:47 -0800, Kuniyuki Iwashima wrote:
> Currently, unix_get_socket() returns struct sock, but after calling
> it, we always cast it to unix_sk().
> 
> Let's return struct unix_sock from unix_get_socket().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
>  include/linux/io_uring.h |  4 ++--
>  include/net/af_unix.h    |  2 +-
>  io_uring/io_uring.c      |  5 +++--
>  net/unix/garbage.c       | 19 +++++++------------
>  net/unix/scm.c           | 26 +++++++++++---------------
>  5 files changed, 24 insertions(+), 32 deletions(-)
> 
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index aefb73eeeebf..be16677f0e4c 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -54,7 +54,7 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>  			      struct iov_iter *iter, void *ioucmd);
>  void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret, ssize_t res2,
>  			unsigned issue_flags);
> -struct sock *io_uring_get_socket(struct file *file);
> +struct unix_sock *io_uring_get_socket(struct file *file);
>  void __io_uring_cancel(bool cancel_all);
>  void __io_uring_free(struct task_struct *tsk);
>  void io_uring_unreg_ringfd(void);
> @@ -111,7 +111,7 @@ static inline void io_uring_cmd_do_in_task_lazy(struct io_uring_cmd *ioucmd,
>  			void (*task_work_cb)(struct io_uring_cmd *, unsigned))
>  {
>  }
> -static inline struct sock *io_uring_get_socket(struct file *file)
> +static inline struct unix_sock *io_uring_get_socket(struct file *file)
>  {
>  	return NULL;
>  }
> diff --git a/include/net/af_unix.h b/include/net/af_unix.h
> index 5a8a670b1920..c628d30ceb19 100644
> --- a/include/net/af_unix.h
> +++ b/include/net/af_unix.h
> @@ -14,7 +14,7 @@ void unix_destruct_scm(struct sk_buff *skb);
>  void io_uring_destruct_scm(struct sk_buff *skb);
>  void unix_gc(void);
>  void wait_for_unix_gc(void);
> -struct sock *unix_get_socket(struct file *filp);
> +struct unix_sock *unix_get_socket(struct file *filp);
>  struct sock *unix_peer_get(struct sock *sk);
>  
>  #define UNIX_HASH_MOD	(256 - 1)
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index ed254076c723..daed897f5975 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -177,13 +177,14 @@ static struct ctl_table kernel_io_uring_disabled_table[] = {
>  };
>  #endif
>  
> -struct sock *io_uring_get_socket(struct file *file)
> +struct unix_sock *io_uring_get_socket(struct file *file)
>  {
>  #if defined(CONFIG_UNIX)
>  	if (io_is_uring_fops(file)) {
>  		struct io_ring_ctx *ctx = file->private_data;
>  
> -		return ctx->ring_sock->sk;
> +		if (ctx->ring_sock->sk)
> +			return unix_sk(ctx->ring_sock->sk);
>  	}
>  #endif
>  	return NULL;
> diff --git a/net/unix/garbage.c b/net/unix/garbage.c
> index db1bb99bb793..4d634f5f6a55 100644
> --- a/net/unix/garbage.c
> +++ b/net/unix/garbage.c
> @@ -105,20 +105,15 @@ static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
>  
>  			while (nfd--) {
>  				/* Get the socket the fd matches if it indeed does so */
> -				struct sock *sk = unix_get_socket(*fp++);
> +				struct unix_sock *u = unix_get_socket(*fp++);
>  
> -				if (sk) {
> -					struct unix_sock *u = unix_sk(sk);
> +				/* Ignore non-candidates, they could have been added
> +				 * to the queues after starting the garbage collection
> +				 */
> +				if (u && test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
> +					hit = true;
>  
> -					/* Ignore non-candidates, they could
> -					 * have been added to the queues after
> -					 * starting the garbage collection
> -					 */
> -					if (test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
> -						hit = true;
> -
> -						func(u);
> -					}
> +					func(u);
>  				}
>  			}
>  			if (hit && hitlist != NULL) {
> diff --git a/net/unix/scm.c b/net/unix/scm.c
> index 4b3979272a81..36ce8fed9acc 100644
> --- a/net/unix/scm.c
> +++ b/net/unix/scm.c
> @@ -21,9 +21,8 @@ EXPORT_SYMBOL(gc_inflight_list);
>  DEFINE_SPINLOCK(unix_gc_lock);
>  EXPORT_SYMBOL(unix_gc_lock);
>  
> -struct sock *unix_get_socket(struct file *filp)
> +struct unix_sock *unix_get_socket(struct file *filp)
>  {
> -	struct sock *u_sock = NULL;
>  	struct inode *inode = file_inode(filp);
>  
>  	/* Socket ? */
> @@ -34,12 +33,13 @@ struct sock *unix_get_socket(struct file *filp)
>  
>  		/* PF_UNIX ? */
>  		if (s && ops && ops->family == PF_UNIX)
> -			u_sock = s;
> -	} else {
> -		/* Could be an io_uring instance */
> -		u_sock = io_uring_get_socket(filp);
> +			return unix_sk(s);
> +
> +		return NULL;
>  	}
> -	return u_sock;
> +
> +	/* Could be an io_uring instance */
> +	return io_uring_get_socket(filp);
>  }
>  EXPORT_SYMBOL(unix_get_socket);
>  
> @@ -48,13 +48,11 @@ EXPORT_SYMBOL(unix_get_socket);
>   */
>  void unix_inflight(struct user_struct *user, struct file *fp)
>  {
> -	struct sock *s = unix_get_socket(fp);
> +	struct unix_sock *u = unix_get_socket(fp);
>  
>  	spin_lock(&unix_gc_lock);
>  
> -	if (s) {
> -		struct unix_sock *u = unix_sk(s);
> -
> +	if (u) {
>  		if (!u->inflight) {
>  			BUG_ON(!list_empty(&u->link));
>  			list_add_tail(&u->link, &gc_inflight_list);
> @@ -71,13 +69,11 @@ void unix_inflight(struct user_struct *user, struct file *fp)
>  
>  void unix_notinflight(struct user_struct *user, struct file *fp)
>  {
> -	struct sock *s = unix_get_socket(fp);
> +	struct unix_sock *u = unix_get_socket(fp);
>  
>  	spin_lock(&unix_gc_lock);
>  
> -	if (s) {
> -		struct unix_sock *u = unix_sk(s);
> -
> +	if (u) {
>  		BUG_ON(!u->inflight);
>  		BUG_ON(list_empty(&u->link));
>  

Adding the io_uring peoples to the recipient list for awareness. I
guess this deserves an explicit ack from them.

Cheers,

Paolo