linux-kernel - Observation of a memory leak with commit e98e49b2bbf7 ("io

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Message-ID: <CAKXUXMzHUi3q4K-OpiBKyMAsQ2K=FOsVzULC76v05nCUKNCA+Q@mail.gmail.com>
Date:   Fri, 7 Jan 2022 16:00:39 +0100
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        io-uring@...r.kernel.org
Subject: Observation of a memory leak with commit e98e49b2bbf7 ("io_uring:
 extend task put optimisations")

Dear Pavel, dear Jens,

In our syzkaller instance running on linux-next,
https://elisa-builder-00.iol.unh.edu/syzkaller-next/, we have been
observing a memory leak in copy_process for quite some time.

It is reproducible on v5.15-rc1, v5.15, v5.16-rc8 and next-20220106:

https://elisa-builder-00.iol.unh.edu/syzkaller-next/crash?id=1169da08a3e72457301987b70bcce62f0f49bdbb

So, it is in mainline, was released and has not been fixed in linux-next yet.

As syzkaller also provides a reproducer, we bisected this memory leak
to be introduced with commit e98e49b2bbf7 ("io_uring: extend task put
optimisations").

Could you please have a look how your commit introduces this memory
leak? We will gladly support testing your fix in case help is needed.

Best regards,

Lukas