pty: Fix lock inversion
The ptmx_open path takes the tty and devpts locks in the wrong order because tty_init_dev locks and returns a locked tty. As far as I can tell this is actually safe anyway because the tty being returned is new so nobody can get a reference to lock it at this point. However we don't even need the devpts lock at this point, it's only held as a byproduct of the way the locks were pushe down. Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -633,7 +633,6 @@ static int ptmx_open(struct inode *inode, struct file *filp)
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mutex_unlock(&devpts_mutex);
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mutex_unlock(&devpts_mutex);
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mutex_lock(&tty_mutex);
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mutex_lock(&tty_mutex);
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mutex_lock(&devpts_mutex);
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tty = tty_init_dev(ptm_driver, index);
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tty = tty_init_dev(ptm_driver, index);
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if (IS_ERR(tty)) {
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if (IS_ERR(tty)) {
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@ -643,7 +642,6 @@ static int ptmx_open(struct inode *inode, struct file *filp)
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/* The tty returned here is locked so we can safely
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/* The tty returned here is locked so we can safely
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drop the mutex */
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drop the mutex */
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mutex_unlock(&devpts_mutex);
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mutex_unlock(&tty_mutex);
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mutex_unlock(&tty_mutex);
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set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
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set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
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