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commit 6827738dc684a87ad54ebba3ae7f3d7c977698eb upstream.
After the patch to restrict the use of mmap() to CAP_SYS_RAWIO for
the currently existing devices, most applications can no longer make
use of the accelerators as in production "you don't run things as root".
To keep the DSA and IAA accelerators usable, hook up a write() method
so that applications can still submit work. In the write method,
sufficient input validation is performed to avoid the security issue
that required the mmap CAP_SYS_RAWIO check.
One complication is that the DSA device allows for indirect ("batched")
descriptors. There is no reasonable way to do the input validation
on these indirect descriptors so the write() method will not allow these
to be submitted to the hardware on affected hardware, and the sysfs
enumeration of support for the opcode is also removed.
Early performance data shows that the performance delta for most common
cases is within the noise.
Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.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.
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.