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request_queue->queue_flags is unsigned long, which is 8-bytes on 64-bit architectures. Most queue flag modifications occur through bit field helpers, but default flags can be logically OR'd via the QUEUE_FLAG_MQ_DEFAULT mask. If this mask happens to include bit 31, the assignment can sign extend the field and set all upper 32 bits. This exact problem has been observed on a downstream kernel that happens to use bit 31 for QUEUE_FLAG_NOWAIT. This is not an immediate problem for current upstream because bit 31 is not included in the default flag assignment (and is not used at all, actually). Regardless, fix up the QUEUE_FLAG_MQ_DEFAULT mask definition to avoid the landmine in the future. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20221003133534.1075582-1-bfoster@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.