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When an external USB synth is unplugged while the module is loaded, we get a null pointer deref. This is because the tty disappears while speakup tries to use to to communicate with the synth. This patch fixes it by checking tty for null before using it. Since tty can become null between the check and its usage, a mutex is introduced. tty usage is now surrounded by the mutex, as is the code in speakup_ldisc_close which sets the tty to null. The mutex also serialises calls to tty from speakup code. In case of tty being null, this sets synth->alive to zero and restarts ttys in case they were stopped by speakup. Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com> Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.