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From:   Ruihan Li <lrh2000@pku.edu.cn>
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     linux-bluetooth@vger.kernel.org, Ruihan Li <lrh2000@pku.edu.cn>
Subject: Re: [PATCH v3 1/4] Bluetooth: Fix potential double free caused by hci_conn_unlink
Date:   Wed,  3 May 2023 21:34:06 +0800
Message-Id: <20230503133406.167517-1-lrh2000@pku.edu.cn>
In-Reply-To: <20230502212527.1662896-1-luiz.dentz@gmail.com>
References: <20230502212527.1662896-1-luiz.dentz@gmail.com>
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Hi Luiz,

On Tue,  2 May 2023 14:25:24 -0700, Luiz Augusto von Dentz wrote:
> From: Ruihan Li <lrh2000@pku.edu.cn>
> 
> The hci_conn_unlink function is being called by hci_conn_del, which
> means it should not call hci_conn_del with the input parameter conn
> again. If it does, conn may have already been released when
> hci_conn_unlink returns, leading to potential UAF and double-free
> issues.
> 
> This patch resolves the problem by modifying hci_conn_unlink to release
> only conn's child links when necessary, but never release conn itself.
> 
> Reported-by: syzbot+690b90b14f14f43f4688@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/
> Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
> Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
> Reported-by: syzbot+690b90b14f14f43f4688@syzkaller.appspotmail.com
> Reported-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
> Reported-by: syzbot+8bb72f86fc823817bc5d@syzkaller.appspotmail.com

I don't think these tags are properly inserted in commit messages, are they?

> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---
>  net/bluetooth/hci_conn.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index 640b951bf40a..70e1655a9df6 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1083,8 +1083,18 @@ static void hci_conn_unlink(struct hci_conn *conn)
>  	if (!conn->parent) {
>  		struct hci_link *link, *t;
>  
> -		list_for_each_entry_safe(link, t, &conn->link_list, list)
> -			hci_conn_unlink(link->conn);
> +		list_for_each_entry_safe(link, t, &conn->link_list, list) {
> +			struct hci_conn *child = link->conn;
> +
> +			hci_conn_unlink(child);
> +
> +			/* Due to race, SCO connection might be not established
> +			 * yet at this point. Delete it now, otherwise it is
> +			 * possible for it to be stuck and can't be deleted.
> +			 */
> +			if (child->handle == HCI_CONN_HANDLE_UNSET)
> +				hci_conn_del(child);
> +		}
>  
>  		return;
>  	}
> @@ -1100,13 +1110,6 @@ static void hci_conn_unlink(struct hci_conn *conn)
>  
>  	kfree(conn->link);
>  	conn->link = NULL;
> -
> -	/* Due to race, SCO connection might be not established
> -	 * yet at this point. Delete it now, otherwise it is
> -	 * possible for it to be stuck and can't be deleted.
> -	 */
> -	if (conn->handle == HCI_CONN_HANDLE_UNSET)
> -		hci_conn_del(conn);
>  }
>  
>  int hci_conn_del(struct hci_conn *conn)
> -- 
> 2.40.0

Thanks,
Ruihan Li