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

[ Upstream commit 47b2116e54b4a854600341487e8b55249e926324 ]

After an bind/unbind cycle, the acm->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.

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
Call trace:
 usb_ep_free_request+0x2c/0xec
 gs_free_req+0x30/0x44
 acm_bind+0x1b8/0x1f4
 usb_add_function+0xcc/0x1f0
 configfs_composite_bind+0x468/0x588
 gadget_bind_driver+0x104/0x270
 really_probe+0x190/0x374
 __driver_probe_device+0xa0/0x12c
 driver_probe_device+0x3c/0x218
 __device_attach_driver+0x14c/0x188
 bus_for_each_drv+0x10c/0x168
 __device_attach+0xfc/0x198
 device_initial_probe+0x14/0x24
 bus_probe_device+0x94/0x11c
 device_add+0x268/0x48c
 usb_add_gadget+0x198/0x28c
 dwc3_gadget_init+0x700/0x858
 __dwc3_set_mode+0x3cc/0x664
 process_scheduled_works+0x1d8/0x488
 worker_thread+0x244/0x334
 kthread+0x114/0x1bc
 ret_from_fork+0x10/0x20

Fixes: 1f1ba11b6494 ("usb gadget: issue notifications from ACM function")
Cc: stable@kernel.org
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://lore.kernel.org/r/20250916-ready-v1-4-4997bf277548@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250916-ready-v1-4-4997bf277548@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_acm.c b/drivers/usb/gadget/function/f_acm.c
index 349945e064bba3c0fbbaf0efc4c7a2c2d31d4612..bc4118d0e4fff9598aff8053e1afb8bfcc174619 100644 (file)
--- a/drivers/usb/gadget/function/f_acm.c
+++ b/drivers/usb/gadget/function/f_acm.c
@@ -11,12 +11,15 @@
 
 /* #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/err.h>
 
+#include <linux/usb/gadget.h>
+
 #include "u_serial.h"
 
 
@@ -612,6 +615,7 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
        struct usb_string       *us;
        int                     status;
        struct usb_ep           *ep;
+       struct usb_request      *request __free(free_usb_request) = NULL;
 
        /* REVISIT might want instance-specific strings to help
         * distinguish instances ...
@@ -629,7 +633,7 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
        /* allocate instance-specific interface IDs, and patch descriptors */
        status = usb_interface_id(c, f);
        if (status < 0)
-               goto fail;
+               return status;
        acm->ctrl_id = status;
        acm_iad_descriptor.bFirstInterface = status;
 
@@ -638,40 +642,38 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
 
        status = usb_interface_id(c, f);
        if (status < 0)
-               goto fail;
+               return status;
        acm->data_id = status;
 
        acm_data_interface_desc.bInterfaceNumber = status;
        acm_union_desc.bSlaveInterface0 = status;
        acm_call_mgmt_descriptor.bDataInterface = status;
 
-       status = -ENODEV;
-
        /* allocate instance-specific endpoints */
        ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_in_desc);
        if (!ep)
-               goto fail;
+               return -ENODEV;
        acm->port.in = ep;
 
        ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_out_desc);
        if (!ep)
-               goto fail;
+               return -ENODEV;
        acm->port.out = ep;
 
        ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_notify_desc);
        if (!ep)
-               goto fail;
+               return -ENODEV;
        acm->notify = ep;
 
        /* allocate notification */
-       acm->notify_req = gs_alloc_req(ep,
-                       sizeof(struct usb_cdc_notification) + 2,
-                       GFP_KERNEL);
-       if (!acm->notify_req)
-               goto fail;
+       request = gs_alloc_req(ep,
+                              sizeof(struct usb_cdc_notification) + 2,
+                              GFP_KERNEL);
+       if (!request)
+               return -ENODEV;
 
-       acm->notify_req->complete = acm_cdc_notify_complete;
-       acm->notify_req->context = acm;
+       request->complete = acm_cdc_notify_complete;
+       request->context = acm;
 
        /* support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
@@ -688,7 +690,9 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
        status = usb_assign_descriptors(f, acm_fs_function, acm_hs_function,
                        acm_ss_function, acm_ss_function);
        if (status)
-               goto fail;
+               return status;
+
+       acm->notify_req = no_free_ptr(request);
 
        dev_dbg(&cdev->gadget->dev,
                "acm ttyGS%d: %s speed IN/%s OUT/%s NOTIFY/%s\n",
@@ -698,14 +702,6 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
                acm->port.in->name, acm->port.out->name,
                acm->notify->name);
        return 0;
-
-fail:
-       if (acm->notify_req)
-               gs_free_req(acm->notify, acm->notify_req);
-
-       ERROR(cdev, "%s/%p: can't bind, err %d\n", f->name, f, status);
-
-       return status;
 }
 
 static void acm_unbind(struct usb_configuration *c, struct usb_function *f)