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From:   Ming Lei <tom.leiming@gmail.com>
Date:   Thu, 11 Jul 2019 17:21:54 +0800
Message-ID: <CACVXFVO-gwVhZRajRx41_sYJKDTX2qZUnZVRXCB0NcegVVTGVw@mail.gmail.com>
Subject: Re: [PATCH] block/bio-integrity: fix a memory leak bug
To:     Wenwen Wang <wang6495@umn.edu>
Cc:     Wenwen Wang <wenwen@cs.uga.edu>, Jens Axboe <axboe@kernel.dk>,
        "open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Thu, Jul 11, 2019 at 3:36 PM Wenwen Wang <wang6495@umn.edu> wrote:
>
> From: Wenwen Wang <wenwen@cs.uga.edu>
>
> In bio_integrity_prep(), a kernel buffer is allocated through kmalloc() to
> hold integrity metadata. Later on, the buffer will be attached to the bio
> structure through bio_integrity_add_page(), which returns the number of
> bytes of integrity metadata attached. Due to unexpected situations,
> bio_integrity_add_page() may return 0. As a result, bio_integrity_prep()
> needs to be terminated with 'false' returned to indicate this error.
> However, the allocated kernel buffer is not freed on this execution path,
> leading to a memory leak.
>
> To fix this issue, free the allocated buffer before returning from
> bio_integrity_prep().
>
> Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
> ---
>  block/bio-integrity.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio-integrity.c b/block/bio-integrity.c
> index 4db6208..bfae10c 100644
> --- a/block/bio-integrity.c
> +++ b/block/bio-integrity.c
> @@ -276,8 +276,10 @@ bool bio_integrity_prep(struct bio *bio)
>                 ret = bio_integrity_add_page(bio, virt_to_page(buf),
>                                              bytes, offset);
>
> -               if (ret == 0)
> +               if (ret == 0) {
> +                       kfree(buf);
>                         return false;
> +               }

This way may not be enough, and the bio payload needs to be freed.

And you may refer to the error handling for 'IS_ERR(bip)', and bio->bi_status
needs to be set, and bio_endio() needs to be called too.


Thanks,
Ming Lei