Re: [PATCH] shared/gatt-server: Fix crash on read multiple

[Szymon Janc <szymon.janc@codecoup.pl>]

On Tuesday, 13 March 2018 08:47:27 CET Szymon Janc wrote:
> When read multiple includes external characteristic, call to
> gatt_db_attribute_read's complete callback is asynchronous.
> 
> Fix following crash:
> Use of uninitialised value of size 8
>    at 0x49718A: read_multiple_complete_cb (gatt-server.c:994)
>    by 0x498999: pending_read_result (gatt-db.c:136)
>    by 0x49A84B: gatt_db_attribute_read_result (gatt-db.c:1787)
>    by 0x451F4C: read_reply_cb (gatt-database.c:1712)
>    by 0x48B221: method_call_reply (client.c:972)
>    by 0x53AB601: ??? (in /usr/lib64/libdbus-1.so.3.19.3)
>    by 0x53AEF7E: dbus_connection_dispatch (in
> /usr/lib64/libdbus-1.so.3.19.3) by 0x486FEF: message_dispatch
> (mainloop.c:72)
>    by 0x50CB576: ??? (in /usr/lib64/libglib-2.0.so.0.5400.3)
>    by 0x50CEB76: g_main_context_dispatch (in
> /usr/lib64/libglib-2.0.so.0.5400.3) by 0x50CEF1F: ??? (in
> /usr/lib64/libglib-2.0.so.0.5400.3)
>    by 0x50CF231: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.5400.3)
> 
> Invalid read of size 8
>    at 0x49718A: read_multiple_complete_cb (gatt-server.c:994)
>    by 0x498999: pending_read_result (gatt-db.c:136)
>    by 0x49A84B: gatt_db_attribute_read_result (gatt-db.c:1787)
>    by 0x451F4C: read_reply_cb (gatt-database.c:1712)
>    by 0x48B221: method_call_reply (client.c:972)
>    by 0x53AB601: ??? (in /usr/lib64/libdbus-1.so.3.19.3)
>    by 0x53AEF7E: dbus_connection_dispatch (in
> /usr/lib64/libdbus-1.so.3.19.3) by 0x486FEF: message_dispatch
> (mainloop.c:72)
>    by 0x50CB576: ??? (in /usr/lib64/libglib-2.0.so.0.5400.3)
>    by 0x50CEB76: g_main_context_dispatch (in
> /usr/lib64/libglib-2.0.so.0.5400.3) by 0x50CEF1F: ??? (in
> /usr/lib64/libglib-2.0.so.0.5400.3)
>    by 0x50CF231: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.5400.3)
>  Address 0x8 is not stack'd, malloc'd or (recently) free'd
> ---
>  src/shared/gatt-server.c | 44 ++++++++++++++++++++++----------------------
>  1 file changed, 22 insertions(+), 22 deletions(-)
> 
> diff --git a/src/shared/gatt-server.c b/src/shared/gatt-server.c
> index a986c5295..faa56abeb 100644
> --- a/src/shared/gatt-server.c
> +++ b/src/shared/gatt-server.c
> @@ -965,10 +965,8 @@ struct read_multiple_resp_data {
>  static void read_multiple_resp_data_free(struct read_multiple_resp_data
> *data) {
>  	free(data->handles);
> -	data->handles = NULL;
> -
>  	free(data->rsp_data);
> -	data->rsp_data = NULL;
> +	free(data);
>  }
> 
>  static void read_multiple_complete_cb(struct gatt_db_attribute *attr, int
> err, @@ -1045,38 +1043,38 @@ static void read_multiple_cb(uint8_t opcode,
> const void *pdu, {
>  	struct bt_gatt_server *server = user_data;
>  	struct gatt_db_attribute *attr;
> -	struct read_multiple_resp_data data;
> +	struct read_multiple_resp_data *data = NULL;
>  	uint8_t ecode = BT_ATT_ERROR_UNLIKELY;
>  	size_t i = 0;
> 
> -	data.handles = NULL;
> -	data.rsp_data = NULL;
> -
>  	if (length < 4) {
>  		ecode = BT_ATT_ERROR_INVALID_PDU;
>  		goto error;
>  	}
> 
> -	data.server = server;
> -	data.num_handles = length / 2;
> -	data.cur_handle = 0;
> -	data.mtu = bt_att_get_mtu(server->att);
> -	data.length = 0;
> -	data.rsp_data = malloc(data.mtu - 1);
> -
> -	if (!data.rsp_data)
> +	data = new0(struct read_multiple_resp_data, 1);
> +	data->handles = NULL;
> +	data->rsp_data = NULL;
> +	data->server = server;
> +	data->num_handles = length / 2;
> +	data->cur_handle = 0;
> +	data->mtu = bt_att_get_mtu(server->att);
> +	data->length = 0;
> +	data->rsp_data = malloc(data->mtu - 1);
> +
> +	if (!data->rsp_data)
>  		goto error;
> 
> -	data.handles = new0(uint16_t, data.num_handles);
> +	data->handles = new0(uint16_t, data->num_handles);
> 
> -	for (i = 0; i < data.num_handles; i++)
> -		data.handles[i] = get_le16(pdu + i * 2);
> +	for (i = 0; i < data->num_handles; i++)
> +		data->handles[i] = get_le16(pdu + i * 2);
> 
>  	util_debug(server->debug_callback, server->debug_data,
>  			"Read Multiple Req - %zu handles, 1st: 0x%04x",
> -			data.num_handles, data.handles[0]);
> +			data->num_handles, data->handles[0]);
> 
> -	attr = gatt_db_get_attribute(server->db, data.handles[0]);
> +	attr = gatt_db_get_attribute(server->db, data->handles[0]);
> 
>  	if (!attr) {
>  		ecode = BT_ATT_ERROR_INVALID_HANDLE;
> @@ -1084,11 +1082,13 @@ static void read_multiple_cb(uint8_t opcode, const
> void *pdu, }
> 
>  	if (gatt_db_attribute_read(attr, 0, opcode, server->att,
> -					read_multiple_complete_cb, &data))
> +					read_multiple_complete_cb, data))
>  		return;
> 
>  error:
> -	read_multiple_resp_data_free(&data);
> +	if (data)
> +		read_multiple_resp_data_free(data);
> +
>  	bt_att_send_error_rsp(server->att, opcode, 0, ecode);
>  }

Applied.

-- 
pozdrawiam
Szymon Janc