ac0f7d4258
Hyper-V Interrupt Message Page (SIMP) has 16 256-byte slots for messages. Each message comes with a header (16 bytes) which specifies the payload length (up to 240 bytes). vmbus_on_msg_dpc(), however, doesn't look at the real message length and copies the whole slot to a temporary buffer before passing it to message handlers. This is potentially dangerous as hypervisor doesn't have to clean the whole slot when putting a new message there and a message handler can get access to some data which belongs to a previous message. Note, this is not currently a problem because all message handlers are in-kernel but eventually we may e.g. get this exported to userspace. Note also, that this is not a performance critical path: messages (unlike events) represent rare events so it doesn't really matter (from performance point of view) if we copy too much. Fix the issue by taking into account the real message length. The temporary buffer allocated by vmbus_on_msg_dpc() remains fixed size for now. Also, check that the supplied payload length is valid (<= 240 bytes). Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Link: https://lore.kernel.org/r/20200406104154.45010-2-vkuznets@redhat.com Signed-off-by: Wei Liu <wei.liu@kernel.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.
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.