linux-kernel - [BUG] io_uring: defer logic based on shared data

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Date:   Fri, 25 Oct 2019 12:55:25 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [BUG] io_uring: defer logic based on shared data

I found 2 problems with __io_sequence_defer().

1. it uses @sq_dropped, but doesn't consider @cq_overflow
2. @sq_dropped and @cq_overflow are write-shared with userspace, so
it can be maliciously changed.

see sent liburing test (test/defer *_hung()), which left an unkillable
process for me

-- 
Yours sincerely,
Pavel Begunkov

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