From: Christoph Hellwig <hch@infradead.org>
To: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>,
axboe@kernel.dk, linux-block@vger.kernel.org,
io-uring@vger.kernel.org
Subject: Re: [PATCH 1/1] block: Manage bio references so the bio persists until necessary
Date: Mon, 3 Feb 2020 23:51:24 -0800 [thread overview]
Message-ID: <20200204075124.GA29349@infradead.org> (raw)
In-Reply-To: <aaecd43b-dd44-f6c5-4e2d-1772cf135d2a@oracle.com>
On Mon, Feb 03, 2020 at 01:07:48PM -0800, Bijan Mottahedeh wrote:
> My concern is with the code below for the single bio async case:
>
> qc = submit_bio(bio);
>
> if (polled)
> WRITE_ONCE(iocb->ki_cookie, qc);
>
> The bio/dio can be freed before the the cookie is written which is what I'm
> seeing, and I thought this may lead to a scenario where that iocb request
> could be completed, freed, reallocated, and resubmitted in io_uring layer;
> i.e., I thought the cookie could be written into the wrong iocb.
I think we do have a potential use after free of the iocb here.
But taking a bio reference isn't going to help with that, as the iocb
and bio/dio life times are unrelated.
I vaguely remember having that discussion with Jens a while ago, and
tried to pass a pointer to the qc to submit_bio so that we can set
it at submission time, but he came up with a reason why that might not
be required. I'd have to dig out all notes unless Jens remembers
better.
next prev parent reply other threads:[~2020-02-04 7:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 3:23 [PATCH 0/1] block: Manage bio references so the bio persists until necessary Bijan Mottahedeh
2020-01-31 3:23 ` [PATCH 1/1] " Bijan Mottahedeh
2020-01-31 6:42 ` Christoph Hellwig
2020-01-31 18:08 ` Bijan Mottahedeh
2020-02-03 8:34 ` Christoph Hellwig
2020-02-03 21:07 ` Bijan Mottahedeh
2020-02-04 7:51 ` Christoph Hellwig [this message]
2020-02-04 20:59 ` Jens Axboe
2020-02-04 22:41 ` Bijan Mottahedeh
2020-02-24 23:32 ` Bijan Mottahedeh
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