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In normal queue cleanup path, hctx is released after request queue is freed, see blk_mq_release(). However, in __blk_mq_update_nr_hw_queues(), hctx may be freed because of hw queues shrinking. This way is easy to cause use-after-free, because: one implicit rule is that it is safe to call almost all block layer APIs if the request queue is alive; and one hctx may be retrieved by one API, then the hctx can be freed by blk_mq_update_nr_hw_queues(); finally use-after-free is triggered. Fixes this issue by always freeing hctx after releasing request queue. If some hctxs are removed in blk_mq_update_nr_hw_queues(), introduce a per-queue list to hold them, then try to resuse these hctxs if numa node is matched. Cc: Dongli Zhang <dongli.zhang@oracle.com> Cc: James Smart <james.smart@broadcom.com> Cc: Bart Van Assche <bart.vanassche@wdc.com> Cc: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen <martin.petersen@oracle.com>, Cc: Christoph Hellwig <hch@lst.de>, Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>, Reviewed-by: Hannes Reinecke <hare@suse.com> Tested-by: James Smart <james.smart@broadcom.com> Signed-off-by: Ming Lei <ming.lei@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.