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The destruction flow is very complicated here because the cm_id can be
destroyed from the event handler at any time if the device is
hot-removed. This leaves behind a partial ctx with no cm_id in the
xarray, and will let user space leak memory.
Make everything consistent in this flow in all places:
- Return the xarray back to XA_ZERO_ENTRY before beginning any
destruction. The thread that reaches this first is responsible to
kfree, everyone else does nothing.
- Test the xarray during the special hot-removal case to block the
queue_work, this has much simpler locking and doesn't require a
'destroying'
- Fix the ref initialization so that it is only positive if cm_id !=
NULL, then rely on that to guide the destruction process in all cases.
Now the new ucma_destroy_private_ctx() can be called in all places that
want to free the ctx, including all the error unwinds, and none of the
details are missed.
Fixes: a1d33b70db ("RDMA/ucma: Rework how new connections are passed through event delivery")
Link: https://lore.kernel.org/r/20210105111327.230270-1-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
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.