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To:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
From:   Pavel Begunkov <asml.silence@gmail.com>
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Subject: [BUG] io_uring: defer logic based on shared data
Message-ID: <5badf1c0-9a7d-0950-2943-ff8db33e0929@gmail.com>
Date:   Fri, 25 Oct 2019 12:55:25 +0300
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Sender: linux-kernel-owner@vger.kernel.org
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
 linux-kernel@vger.kernel.org
Message-ID: <5badf1c0-9a7d-0950-2943-ff8db33e0929@gmail.com>
Subject: [BUG] io_uring: defer logic based on shared data

--Gs26cYXp9MkxYTYA1qtNoNsNFYOku5ICy
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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

--=20
Yours sincerely,
Pavel Begunkov


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