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While handling the completion queue, keep a local copy of the command id from the DMA-accessible completion entry. This silences a time-of-check to time-of-use (TOCTOU) warning from KF/x[1], with respect to a Thunderclap[2] vulnerability analysis. The double-read impact appears benign. There may be a theoretical window for @command_id to be used as an adversary-controlled array-index-value for mounting a speculative execution attack, but that mitigation is saved for a potential follow-on. A man-in-the-middle attack on the data payload is out of scope for this analysis and is hopefully mitigated by filesystem integrity mechanisms. [1] https://github.com/intel/kernel-fuzzer-for-xen-project [2] http://thunderclap.io/thunderclap-paper-ndss2019.pdf Signed-off-by: Lalithambika Krishna Kumar <lalithambika.krishnakumar@intel.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
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.