598c2d41ff
syzbot is reporting crashes [1] triggered by memory allocation failure at tty_ldisc_get() from tty_ldisc_restore(). While syzbot stops at WARN_ON() due to panic_on_warn == true, panic_on_warn == false will after all trigger an OOPS by dereferencing old->ops->num if IS_ERR(old) == true. We can simplify tty_ldisc_restore() as three calls (old->ops->num, N_TTY, N_NULL) to tty_ldisc_failto() in addition to avoiding possible error pointer dereference. If someone reports kernel panic triggered by forcing all memory allocations for tty_ldisc_restore() to fail, we can consider adding __GFP_NOFAIL for tty_ldisc_restore() case. [1] https://syzkaller.appspot.com/bug?id=6ac359c61e71d22e06db7f8f88243feb11d927e7 Reported-by: syzbot+40b7287c2dc987c48c81@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Alan Cox <alan@llwyncelyn.cymru> Cc: Christoph Hellwig <hch@lst.de> Cc: Michal Hocko <mhocko@suse.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.