usbip: vudc: fix NULL deref in vep_dequeue()

vep_alloc_request() wasn't initializing vrequest->udc, so cancellations
on the FunctionFS AIO path were arriving in vep_dequeue without a valid
UDC reference.

Since vrequest->udc is never actually properly used anywhere, we opt to
remove it, and update vep_dequeue to obtain a reference to the udc with
ep_to_vudc(), consistent with the other vep_ ops.

AFAICT this bug has existed for ~10 years. Seems that nobody has really
stressed the FunctionFS AIO path on usbip's vudc.

I tested this fix in a QEMU aarch64 guest driving FunctionFS endpoints
via AIO. Before the fix, running `usbip attach` from the host would
cause the guest to oops with the following backtrace:

Call trace:
 vep_dequeue+0x1c/0xe4 (P)
 usb_ep_dequeue+0x14/0x20
 ffs_aio_cancel+0x24/0x34
 __arm64_sys_io_cancel+0xb0/0x124
 do_el0_svc+0x68/0x100
 el0_svc+0x18/0x5c
 el0t_64_sync_handler+0x98/0xdc
 el0t_64_sync+0x154/0x158

Assisted-by: opencode:openai/gpt-5.5
Cc: stable <stable@kernel.org>
Fixes: b6a0ca111867 ("usbip: vudc: Add UDC specific ops")
Reviewed-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: Sam Day <me@samcday.com>
Link: https://patch.msgid.link/20260626-usbip-vudc-deque-fix-v3-1-98c2dc4d6a48@samcday.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/usbip/vudc.h b/drivers/usb/usbip/vudc.h
index faf61c9c6a9894269f3b171467e7bad238406248..5ef0e7d9b23ad4718d2a31a671629f26dd06d4eb 100644 (file)
--- a/drivers/usb/usbip/vudc.h
+++ b/drivers/usb/usbip/vudc.h
@@ -38,7 +38,6 @@ struct vep {
 
 struct vrequest {
        struct usb_request req;
-       struct vudc *udc;
        struct list_head req_entry; /* Request queue */
 };
 

diff --git a/drivers/usb/usbip/vudc_dev.c b/drivers/usb/usbip/vudc_dev.c
index c5f079c5a1ea5cc4899e63c39eb8e4060dd7af7d..5ef88117965d1a22f0cb9b9ccfca3329e0a223af 100644 (file)
--- a/drivers/usb/usbip/vudc_dev.c
+++ b/drivers/usb/usbip/vudc_dev.c
@@ -333,7 +333,6 @@ static int vep_queue(struct usb_ep *_ep, struct usb_request *_req,
 static int vep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
 {
        struct vep *ep;
-       struct vrequest *req;
        struct vudc *udc;
        struct vrequest *lst;
        unsigned long flags;
@@ -343,8 +342,7 @@ static int vep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
                return ret;
 
        ep = to_vep(_ep);
-       req = to_vrequest(_req);
-       udc = req->udc;
+       udc = ep_to_vudc(ep);
 
        if (!udc->driver)
                return -ESHUTDOWN;