linux-kernel - Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer dereference in amp_read_loc_assoc_final

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Date:   Wed, 3 Mar 2021 09:21:41 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Peilin Ye <yepeilin.cs@...il.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Andrei Emeltchenko <andrei.emeltchenko@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, gtiwari@...hat.com,
        syzbot+f4fb0eaafdb51c32a153@...kaller.appspotmail.com
Subject: Re: [Linux-kernel-mentees] [PATCH net] Bluetooth: Fix NULL pointer
 dereference in amp_read_loc_assoc_final_data()

On Sat, Aug 8, 2020 at 6:06 AM Peilin Ye <yepeilin.cs@...il.com> wrote:
>
> Prevent amp_read_loc_assoc_final_data() from dereferencing `mgr` as NULL.
>
> Reported-and-tested-by: syzbot+f4fb0eaafdb51c32a153@...kaller.appspotmail.com
> Fixes: 9495b2ee757f ("Bluetooth: AMP: Process Chan Selected event")
> Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
> ---
>  net/bluetooth/amp.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/net/bluetooth/amp.c b/net/bluetooth/amp.c
> index 9c711f0dfae3..be2d469d6369 100644
> --- a/net/bluetooth/amp.c
> +++ b/net/bluetooth/amp.c
> @@ -297,6 +297,9 @@ void amp_read_loc_assoc_final_data(struct hci_dev *hdev,
>         struct hci_request req;
>         int err;
>
> +       if (!mgr)
> +               return;
> +
>         cp.phy_handle = hcon->handle;
>         cp.len_so_far = cpu_to_le16(0);
>         cp.max_len = cpu_to_le16(hdev->amp_assoc_size);

Not sure what happened here, but the merged patch somehow has a
different author and no Reported-by tag:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e8bd76ede155fd54d8c41d045dda43cd3174d506
so let's tell syzbot what fixed it manually:
#syz fix:
Bluetooth: Fix null pointer dereference in amp_read_loc_assoc_final_data