Pavel Begunkov 1bcb8c5d65 io_uring: fix feeding io-wq with uninit reqs
io_steal_work() can't be sure that @nxt has req->work properly set, so we
can't pass it to io-wq as is.

A dirty quick fix -- drag it through io_req_task_queue(), and always
return NULL from io_steal_work().

e.g.

[   50.770161] BUG: kernel NULL pointer dereference, address: 00000000
[   50.770164] #PF: supervisor write access in kernel mode
[   50.770164] #PF: error_code(0x0002) - not-present page
[   50.770168] CPU: 1 PID: 1448 Comm: io_wqe_worker-0 Tainted: G
	I       5.8.0-rc2-00035-g2237d76530eb-dirty #494
[   50.770172] RIP: 0010:override_creds+0x19/0x30
...
[   50.770183]  io_worker_handle_work+0x25c/0x430
[   50.770185]  io_wqe_worker+0x2a0/0x350
[   50.770190]  kthread+0x136/0x180
[   50.770194]  ret_from_fork+0x22/0x30

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-06-28 08:10:17 -06:00
2020-06-21 15:45:29 -07:00

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.
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