linux-kernel - Re: [PATCH v2] block: Fix use-after-free in blkdev

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Message-ID: <CA+icZUVFQaXGVtfGEO2=covaaRR2iKOTASsLEXv7+CsV5ibShQ@mail.gmail.com>
Date:   Fri, 5 Jun 2020 13:10:57 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Jason Yan <yanaijie@...wei.com>, Jan Kara <jack@...e.cz>,
        Markus Elfring <Markus.Elfring@....de>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hulkci@...wei.com, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: [PATCH v2] block: Fix use-after-free in blkdev_get()

On Fri, Jun 5, 2020 at 11:46 AM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> A lot of maintainers have blocked Markus and asked him to stop trying
> to help people write commit message.  Saying "bdev" instead of "block
> device" is more clear so your original message was better.
>
> The Fixes tag is a good idea though:
>
> Fixes: 89e524c04fa9 ("loop: Fix mount(2) failure due to race with LOOP_SET_FD")
>
> It broke last July.  Before that, we used to check if __blkdev_get()
> failed before dereferencing "bdev".
>
> I wonder if maybe the best fix is to re-add the "if (!res) " check back
> to blkdev_get().  The __blkdev_get() looks like it can also free "whole"
> though if it calls itself recursively and I don't really know this code
> so I can't say for sure...
>

In things of Fixes: tag...

For the first hunk I found:

commit 8266602033d6adc6d10cb8811c1fd694767909b0 ("fix bdev leak in
block_dev.c do_open()")

- Sedat -