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commit 8c2f870890fd28e023b0fcf49dcee333f2c8bad7 upstream. The ALSA proc helper manages the child nodes in a linked list, but its addition and deletion is done without any lock. This leads to a corruption if they are operated concurrently. Usually this isn't a problem because the proc entries are added sequentially in the driver probe procedure itself. But the card registrations are done often asynchronously, and the crash could be actually reproduced with syzkaller. This patch papers over it by protecting the link addition and deletion with the parent's mutex. There is "access" mutex that is used for the file access, and this can be reused for this purpose as well. Reported-by: syzbot+48df349490c36f9f54ab@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> 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.