usb: gadget: f_ecm: Refactor bind path to use __free()

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

diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
index 027226325039f0c8eaee27a339513a758c01786b..675d2bc538a45747de601b0fcf2b7b8757642214 100644 (file)
--- a/drivers/usb/gadget/function/f_ecm.c
+++ b/drivers/usb/gadget/function/f_ecm.c
@@ -8,6 +8,7 @@
 
 /* #define VERBOSE_DEBUG */
 
+#include <linux/cleanup.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -15,6 +16,8 @@
 #include <linux/etherdevice.h>
 #include <linux/string_choices.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, struct usb_function *f)
        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, struct usb_function *f)
        /* 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, struct usb_function *f)
 
        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, struct usb_function *f)
         */
        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, struct usb_function *f)
        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, struct usb_function *f)
        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)