tty: fix race in tty_fasync
We need to keep the lock held over the call to __f_setown() to prevent a PID race. Thanks to Al Viro for pointing out the problem, and to Travis for making us look here in the first place. Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Tavis Ormandy <taviso@google.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Julien Tinnes <jln@google.com> Cc: Matt Mackall <mpm@selenic.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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@ -1951,8 +1951,8 @@ static int tty_fasync(int fd, struct file *filp, int on)
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pid = task_pid(current);
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type = PIDTYPE_PID;
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}
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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retval = __f_setown(filp, pid, type, 0);
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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if (retval)
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goto out;
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} else {
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