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Commit 9214407d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'locks-v4.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux 

Pull fasync fix from Jeff Layton:
 "Just a single fix for a deadlock in the fasync handling code that
  Kirill observed while testing.

  The fix is to change the fa_lock to be rwlock_t, and use a read lock
  in kill_fasync_rcu"

* tag 'locks-v4.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  fasync: Fix deadlock between task-context and interrupt-context kill_fasync()
parents eeee3149 7a107c0f

fs/fcntl.c

+7 −8
Original line number Diff line number Diff line
@@ -871,9 +871,9 @@ int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp) 
		if (fa->fa_file != filp)

			continue;



		spin_lock_irq(&fa->fa_lock);

		write_lock_irq(&fa->fa_lock);

		fa->fa_file = NULL;

		spin_unlock_irq(&fa->fa_lock);

		write_unlock_irq(&fa->fa_lock);



		*fp = fa->fa_next;

		call_rcu(&fa->fa_rcu, fasync_free_rcu);
@@ -918,13 +918,13 @@ struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasy 
		if (fa->fa_file != filp)

			continue;



		spin_lock_irq(&fa->fa_lock);

		write_lock_irq(&fa->fa_lock);

		fa->fa_fd = fd;

		spin_unlock_irq(&fa->fa_lock);

		write_unlock_irq(&fa->fa_lock);

		goto out;

	}



	spin_lock_init(&new->fa_lock);

	rwlock_init(&new->fa_lock);

	new->magic = FASYNC_MAGIC;

	new->fa_file = filp;

	new->fa_fd = fd;
@@ -987,14 +987,13 @@ static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band) 
{

	while (fa) {

		struct fown_struct *fown;

		unsigned long flags;



		if (fa->magic != FASYNC_MAGIC) {

			printk(KERN_ERR "kill_fasync: bad magic number in "

			       "fasync_struct!\n");

			return;

		}

		spin_lock_irqsave(&fa->fa_lock, flags);

		read_lock(&fa->fa_lock);

		if (fa->fa_file) {

			fown = &fa->fa_file->f_owner;

			/* Don't send SIGURG to processes which have not set a
@@ -1003,7 +1002,7 @@ static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band) 
			if (!(sig == SIGURG && fown->signum == 0))

				send_sigio(fown, fa->fa_fd, band);

		}

		spin_unlock_irqrestore(&fa->fa_lock, flags);

		read_unlock(&fa->fa_lock);

		fa = rcu_dereference(fa->fa_next);

	}

}

include/linux/fs.h

+1 −1
Original line number Diff line number Diff line
@@ -1250,7 +1250,7 @@ static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl) 
}



struct fasync_struct {

	spinlock_t		fa_lock;

	rwlock_t		fa_lock;

	int			magic;

	int			fa_fd;

	struct fasync_struct	*fa_next; /* singly linked list */