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In vbg_misc_device_ioctl(), the header of the ioctl argument is copied from the userspace pointer 'arg' and saved to the kernel object 'hdr'. Then the 'version', 'size_in', and 'size_out' fields of 'hdr' are verified. Before this commit, after the checks a buffer for the entire request would be allocated and then all data including the verified header would be copied from the userspace 'arg' pointer again. Given that the 'arg' pointer resides in userspace, a malicious userspace process can race to change the data pointed to by 'arg' between the two copies. By doing so, the user can bypass the verifications on the ioctl argument. This commit fixes this by using the already checked copy of the header to fill the header part of the allocated buffer and only copying the remainder of the data from userspace. Signed-off-by: Wenwen Wang <wang6495@umn.edu> Reviewed-by: Hans de Goede <hdegoede@redhat.com> 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.