[PATCH 6.6 030/105] usb: gadget: f_ecm: Refactor bind path to use __free()

Greg Kroah-Hartman
2025-10-21T19:53:45Z

From: Kuen-Han Tsai <khtsai@google.com>

[ Upstream commit 42988380ac67c76bb9dff8f77d7ef3eefd50b7b5 ]

After an bind/unbind cycle, the ecm->notify_req is left stale. If a
subsequent bind fails, the unified error label attempts to free this
stale request, leading to a NULL pointer dereference when accessing
ep->ops->free_request.

Refactor the error handling in the bind path to use the __free()
automatic cleanup mechanism.

Fixes: da741b8c56d6 ("usb ethernet gadget: split CDC Ethernet function")
Cc: stable@kernel.org
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://lore.kernel.org/r/20250916-ready-v1-5-4997bf277548@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250916-ready-v1-5-4997bf277548@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_ecm.c | 48 +++++++++++++++---------------------
1 file changed, 20 insertions(+), 28 deletions(-)

--- a/drivers/usb/gadget/function/f_ecm.c
+++ b/drivers/usb/gadget/function/f_ecm.c
@@ -8,12 +8,15 @@

/* #define VERBOSE_DEBUG */

+#include <linux/cleanup.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/etherdevice.h>

+#include <linux/usb/gadget.h>
+
#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_ecm.h"
@@ -678,6 +681,7 @@ ecm_bind(struct usb_configuration *c, st
struct usb_ep *ep;

struct f_ecm_opts *ecm_opts;
+ struct usb_request *request __free(free_usb_request) = NULL;

if (!can_support_ecm(cdev->gadget))
return -EINVAL;
@@ -711,7 +715,7 @@ ecm_bind(struct usb_configuration *c, st
/* allocate instance-specific interface IDs */
status = usb_interface_id(c, f);
if (status < 0)
- goto fail;
+ return status;
ecm->ctrl_id = status;
ecm_iad_descriptor.bFirstInterface = status;

@@ -720,24 +724,22 @@ ecm_bind(struct usb_configuration *c, st

status = usb_interface_id(c, f);
if (status < 0)
- goto fail;
+ return status;
ecm->data_id = status;

ecm_data_nop_intf.bInterfaceNumber = status;
ecm_data_intf.bInterfaceNumber = status;
ecm_union_desc.bSlaveInterface0 = status;

- status = -ENODEV;
-
/* allocate instance-specific endpoints */
ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_in_desc);
if (!ep)
- goto fail;
+ return -ENODEV;
ecm->port.in_ep = ep;

ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_out_desc);
if (!ep)
- goto fail;
+ return -ENODEV;
ecm->port.out_ep = ep;

/* NOTE: a status/notification endpoint is *OPTIONAL* but we
@@ -746,20 +748,18 @@ ecm_bind(struct usb_configuration *c, st
*/
ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_notify_desc);
if (!ep)
- goto fail;
+ return -ENODEV;
ecm->notify = ep;

- status = -ENOMEM;
-
/* allocate notification request and buffer */
- ecm->notify_req = usb_ep_alloc_request(ep, GFP_KERNEL);
- if (!ecm->notify_req)
- goto fail;
- ecm->notify_req->buf = kmalloc(ECM_STATUS_BYTECOUNT, GFP_KERNEL);
- if (!ecm->notify_req->buf)
- goto fail;
- ecm->notify_req->context = ecm;
- ecm->notify_req->complete = ecm_notify_complete;
+ request = usb_ep_alloc_request(ep, GFP_KERNEL);
+ if (!request)
+ return -ENOMEM;
+ request->buf = kmalloc(ECM_STATUS_BYTECOUNT, GFP_KERNEL);
+ if (!request->buf)
+ return -ENOMEM;
+ request->context = ecm;
+ request->complete = ecm_notify_complete;

/* support all relevant hardware speeds... we expect that when
* hardware is dual speed, all bulk-capable endpoints work at
@@ -778,7 +778,7 @@ ecm_bind(struct usb_configuration *c, st
status = usb_assign_descriptors(f, ecm_fs_function, ecm_hs_function,
ecm_ss_function, ecm_ss_function);
if (status)
- goto fail;
+ return status;

/* NOTE: all that is done without knowing or caring about
* the network link ... which is unavailable to this code
@@ -788,20 +788,12 @@ ecm_bind(struct usb_configuration *c, st
ecm->port.open = ecm_open;
ecm->port.close = ecm_close;

+ ecm->notify_req = no_free_ptr(request);
+
DBG(cdev, "CDC Ethernet: IN/%s OUT/%s NOTIFY/%s\n",
ecm->port.in_ep->name, ecm->port.out_ep->name,
ecm->notify->name);
return 0;
-
-fail:
- if (ecm->notify_req) {
- kfree(ecm->notify_req->buf);
- usb_ep_free_request(ecm->notify, ecm->notify_req);
- }
-
- ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
-
- return status;
}

static inline struct f_ecm_opts *to_f_ecm_opts(struct config_item *item)