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fasync fix for v4.18 

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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()
This commit is contained in:
Linus Torvalds 2018-06-04 13:05:02 -07:00
parent eeee3149aa 7a107c0f55
commit 9214407d12
2 changed files with 8 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
fs/fcntl.c
View File

@ -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);
}
}

2
include/linux/fs.h
View File

@ -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 */