This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD converter[1]. The original developers may have only 3 interfaces device to test so they write 3 here and wait for future change.

During the HSCanT development, we actually used 4 interfaces, so the limitation of 3 is not enough now. But just increase one is not future-proofed. Since the channel index type in gs_host_frame is u8, just make canch[] become a flexible array with a u8 index, so it naturally constraint by U8_MAX and avoid statically allocate 256 pointer for every gs_usb device.

[1]: https://github.com/cherry-embedded/HSCanT-hardware

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices") Reported-by: Runcheng Lu runcheng.lu@hpmicro.com Cc: stable@vger.kernel.org Reviewed-by: Vincent Mailhol mailhol@kernel.org Signed-off-by: Celeste Liu uwu@coelacanthus.name --- Changes in v5: - Reword commit message to match the code better. - Link to v4: https://lore.kernel.org/r/20250930-gs-usb-max-if-v4-1-8e163eb583da@coelacant...

Changes in v4: - Remove redudant typeof(). - Fix type: inteface -> interface. - Link to v3: https://lore.kernel.org/r/20250930-gs-usb-max-if-v3-1-21d97d7f1c34@coelacant...

Changes in v3: - Cc stable should in patch instead of cover letter. - Link to v2: https://lore.kernel.org/r/20250930-gs-usb-max-if-v2-1-2cf9a44e6861@coelacant...

Changes in v2: - Use flexible array member instead of fixed array. - Link to v1: https://lore.kernel.org/r/20250929-gs-usb-max-if-v1-1-e41b5c09133a@coelacant... --- drivers/net/can/usb/gs_usb.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c index c9482d6e947b0c7b033dc4f0c35f5b111e1bfd92..9fb4cbbd6d6dc88f433020eb0417ea53cd0c4d5f 100644 --- a/drivers/net/can/usb/gs_usb.c +++ b/drivers/net/can/usb/gs_usb.c @@ -289,11 +289,6 @@ struct gs_host_frame { #define GS_MAX_RX_URBS 30 #define GS_NAPI_WEIGHT 32

-/* Maximum number of interfaces the driver supports per device. - * Current hardware only supports 3 interfaces. The future may vary. - */ -#define GS_MAX_INTF 3 - struct gs_tx_context { struct gs_can *dev; unsigned int echo_id; @@ -324,7 +319,6 @@ struct gs_can {

/* usb interface struct */ struct gs_usb { - struct gs_can *canch[GS_MAX_INTF]; struct usb_anchor rx_submitted; struct usb_device *udev;

@@ -336,9 +330,11 @@ struct gs_usb {

unsigned int hf_size_rx; u8 active_channels; + u8 channel_cnt;

unsigned int pipe_in; unsigned int pipe_out; + struct gs_can *canch[] __counted_by(channel_cnt); };

/* 'allocate' a tx context. @@ -599,7 +595,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb) }

/* device reports out of range channel id */ - if (hf->channel >= GS_MAX_INTF) + if (hf->channel >= parent->channel_cnt) goto device_detach;

dev = parent->canch[hf->channel]; @@ -699,7 +695,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb) /* USB failure take down all interfaces */ if (rc == -ENODEV) { device_detach: - for (rc = 0; rc < GS_MAX_INTF; rc++) { + for (rc = 0; rc < parent->channel_cnt; rc++) { if (parent->canch[rc]) netif_device_detach(parent->canch[rc]->netdev); } @@ -1460,17 +1456,19 @@ static int gs_usb_probe(struct usb_interface *intf, icount = dconf.icount + 1; dev_info(&intf->dev, "Configuring for %u interfaces\n", icount);

- if (icount > GS_MAX_INTF) { + if (icount > type_max(parent->channel_cnt)) { dev_err(&intf->dev, "Driver cannot handle more that %u CAN interfaces\n", - GS_MAX_INTF); + type_max(parent->channel_cnt)); return -EINVAL; }

- parent = kzalloc(sizeof(*parent), GFP_KERNEL); + parent = kzalloc(struct_size(parent, canch, icount), GFP_KERNEL); if (!parent) return -ENOMEM;

+ parent->channel_cnt = icount; + init_usb_anchor(&parent->rx_submitted);

usb_set_intfdata(intf, parent); @@ -1531,7 +1529,7 @@ static void gs_usb_disconnect(struct usb_interface *intf) return; }

- for (i = 0; i < GS_MAX_INTF; i++) + for (i = 0; i < parent->channel_cnt; i++) if (parent->canch[i]) gs_destroy_candev(parent->canch[i]);

--- base-commit: e5f0a698b34ed76002dc5cff3804a61c80233a7a change-id: 20250929-gs-usb-max-if-a304c83243e5

Best regards,