Thanks Dan for the report !
This is indeed a bug and will be fixed in the subsequent kernel.
Have a nice day,
Gil
On Wed, Apr 17, 2024 at 03:52:34PM +0300, Dan Carpenter wrote:
> Hello Gil Fine,
>
> Commit 25d905d2b819 ("thunderbolt: Allow USB3 bandwidth to be lower
> than maximum supported") from Feb 12, 2024 (linux-next), leads to the
> following Smatch static checker warning:
>
> drivers/thunderbolt/tunnel.c:2113 tb_tunnel_alloc_usb3()
> error: uninitialized symbol 'max_rate'.
>
> drivers/thunderbolt/tunnel.c
> 2061 struct tb_tunnel *tb_tunnel_alloc_usb3(struct tb *tb, struct tb_port *up,
> 2062 struct tb_port *down, int max_up,
> 2063 int max_down)
> 2064 {
> 2065 struct tb_tunnel *tunnel;
> 2066 struct tb_path *path;
> 2067 int max_rate;
> 2068
> 2069 if (!tb_route(down->sw) && (max_up > 0 || max_down > 0)) {
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> The patch adds this condition. If both of these are <= 0 then
> max_rate is uninitialized.
>
> 2070 /*
> 2071 * For USB3 isochronous transfers, we allow bandwidth which is
> 2072 * not higher than 90% of maximum supported bandwidth by USB3
> 2073 * adapters.
> 2074 */
> 2075 max_rate = tb_usb3_max_link_rate(down, up);
> 2076 if (max_rate < 0)
> 2077 return NULL;
> 2078
> 2079 max_rate = max_rate * 90 / 100;
> 2080 tb_port_dbg(up, "maximum required bandwidth for USB3 tunnel %d Mb/s\n",
> 2081 max_rate);
> 2082 }
> 2083
> 2084 tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_USB3);
> 2085 if (!tunnel)
> 2086 return NULL;
> 2087
> 2088 tunnel->activate = tb_usb3_activate;
> 2089 tunnel->src_port = down;
> 2090 tunnel->dst_port = up;
> 2091 tunnel->max_up = max_up;
> 2092 tunnel->max_down = max_down;
> 2093
> 2094 path = tb_path_alloc(tb, down, TB_USB3_HOPID, up, TB_USB3_HOPID, 0,
> 2095 "USB3 Down");
> 2096 if (!path) {
> 2097 tb_tunnel_free(tunnel);
> 2098 return NULL;
> 2099 }
> 2100 tb_usb3_init_path(path);
> 2101 tunnel->paths[TB_USB3_PATH_DOWN] = path;
> 2102
> 2103 path = tb_path_alloc(tb, up, TB_USB3_HOPID, down, TB_USB3_HOPID, 0,
> 2104 "USB3 Up");
> 2105 if (!path) {
> 2106 tb_tunnel_free(tunnel);
> 2107 return NULL;
> 2108 }
> 2109 tb_usb3_init_path(path);
> 2110 tunnel->paths[TB_USB3_PATH_UP] = path;
> 2111
> 2112 if (!tb_route(down->sw)) {
> --> 2113 tunnel->allocated_up = min(max_rate, max_up);
> ^^^^^^^^
> 2114 tunnel->allocated_down = min(max_rate, max_down);
> ^^^^^^^^
> Uninitialized.
>
> 2115
> 2116 tunnel->init = tb_usb3_init;
> 2117 tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
> 2118 tunnel->release_unused_bandwidth =
> 2119 tb_usb3_release_unused_bandwidth;
> 2120 tunnel->reclaim_available_bandwidth =
> 2121 tb_usb3_reclaim_available_bandwidth;
> 2122 }
> 2123
> 2124 return tunnel;
> 2125 }
>
> regards,
> dan carpenter
--
Thanks,
Gil
