[PATCH 6.6 033/105] usb: gadget: f_rndis: Refactor bind path to use __free()

Greg Kroah-Hartman
2025-10-21T19:53:54Z

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

[ Upstream commit 08228941436047bdcd35a612c1aec0912a29d8cd ]

After an bind/unbind cycle, the rndis->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: 45fe3b8e5342 ("usb ethernet gadget: split RNDIS function")
Cc: stable@kernel.org
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://lore.kernel.org/r/20250916-ready-v1-6-4997bf277548@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250916-ready-v1-6-4997bf277548@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_rndis.c | 85 ++++++++++++++--------------------
1 file changed, 35 insertions(+), 50 deletions(-)

--- a/drivers/usb/gadget/function/f_rndis.c
+++ b/drivers/usb/gadget/function/f_rndis.c
@@ -19,6 +19,8 @@

#include <linux/atomic.h>

+#include <linux/usb/gadget.h>
+
#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_rndis.h"
@@ -662,6 +664,8 @@ rndis_bind(struct usb_configuration *c,
struct usb_ep *ep;

struct f_rndis_opts *rndis_opts;
+ struct usb_os_desc_table *os_desc_table __free(kfree) = NULL;
+ struct usb_request *request __free(free_usb_request) = NULL;

if (!can_support_rndis(c))
return -EINVAL;
@@ -669,12 +673,9 @@ rndis_bind(struct usb_configuration *c,
rndis_opts = container_of(f->fi, struct f_rndis_opts, func_inst);

if (cdev->use_os_string) {
- f->os_desc_table = kzalloc(sizeof(*f->os_desc_table),
- GFP_KERNEL);
- if (!f->os_desc_table)
+ os_desc_table = kzalloc(sizeof(*os_desc_table), GFP_KERNEL);
+ if (!os_desc_table)
return -ENOMEM;
- f->os_desc_n = 1;
- f->os_desc_table[0].os_desc = &rndis_opts->rndis_os_desc;
}

rndis_iad_descriptor.bFunctionClass = rndis_opts->class;
@@ -692,16 +693,14 @@ rndis_bind(struct usb_configuration *c,
gether_set_gadget(rndis_opts->net, cdev->gadget);
status = gether_register_netdev(rndis_opts->net);
if (status)
- goto fail;
+ return status;
rndis_opts->bound = true;
}

us = usb_gstrings_attach(cdev, rndis_strings,
ARRAY_SIZE(rndis_string_defs));
- if (IS_ERR(us)) {
- status = PTR_ERR(us);
- goto fail;
- }
+ if (IS_ERR(us))
+ return PTR_ERR(us);
rndis_control_intf.iInterface = us[0].id;
rndis_data_intf.iInterface = us[1].id;
rndis_iad_descriptor.iFunction = us[2].id;
@@ -709,36 +708,30 @@ rndis_bind(struct usb_configuration *c,
/* allocate instance-specific interface IDs */
status = usb_interface_id(c, f);
if (status < 0)
- goto fail;
+ return status;
rndis->ctrl_id = status;
rndis_iad_descriptor.bFirstInterface = status;

rndis_control_intf.bInterfaceNumber = status;
rndis_union_desc.bMasterInterface0 = status;

- if (cdev->use_os_string)
- f->os_desc_table[0].if_id =
- rndis_iad_descriptor.bFirstInterface;
-
status = usb_interface_id(c, f);
if (status < 0)
- goto fail;
+ return status;
rndis->data_id = status;

rndis_data_intf.bInterfaceNumber = status;
rndis_union_desc.bSlaveInterface0 = status;

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

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

/* NOTE: a status/notification endpoint is, strictly speaking,
@@ -747,21 +740,19 @@ rndis_bind(struct usb_configuration *c,
*/
ep = usb_ep_autoconfig(cdev->gadget, &fs_notify_desc);
if (!ep)
- goto fail;
+ return -ENODEV;
rndis->notify = ep;

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

/* support all relevant hardware speeds... we expect that when
* hardware is dual speed, all bulk-capable endpoints work at
@@ -778,7 +769,7 @@ rndis_bind(struct usb_configuration *c,
status = usb_assign_descriptors(f, eth_fs_function, eth_hs_function,
eth_ss_function, eth_ss_function);
if (status)
- goto fail;
+ return status;

rndis->port.open = rndis_open;
rndis->port.close = rndis_close;
@@ -789,9 +780,18 @@ rndis_bind(struct usb_configuration *c,
if (rndis->manufacturer && rndis->vendorID &&
rndis_set_param_vendor(rndis->params, rndis->vendorID,
rndis->manufacturer)) {
- status = -EINVAL;
- goto fail_free_descs;
+ usb_free_all_descriptors(f);
+ return -EINVAL;
+ }
+
+ if (cdev->use_os_string) {
+ os_desc_table[0].os_desc = &rndis_opts->rndis_os_desc;
+ os_desc_table[0].if_id = rndis_iad_descriptor.bFirstInterface;
+ f->os_desc_table = no_free_ptr(os_desc_table);
+ f->os_desc_n = 1;
+
}
+ rndis->notify_req = no_free_ptr(request);

/* NOTE: all that is done without knowing or caring about
* the network link ... which is unavailable to this code
@@ -802,21 +802,6 @@ rndis_bind(struct usb_configuration *c,
rndis->port.in_ep->name, rndis->port.out_ep->name,
rndis->notify->name);
return 0;
-
-fail_free_descs:
- usb_free_all_descriptors(f);
-fail:
- kfree(f->os_desc_table);
- f->os_desc_n = 0;
-
- if (rndis->notify_req) {
- kfree(rndis->notify_req->buf);
- usb_ep_free_request(rndis->notify, rndis->notify_req);
- }
-
- ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
-
- return status;
}

void rndis_borrow_net(struct usb_function_instance *f, struct net_device *net)