6.6-stable review patch. If anyone has any objections, please let me know.
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From: Kuen-Han Tsai khtsai@google.com
[ 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 --- drivers/usb/gadget/function/f_acm.c | 42 ++++++++++++++++-------------------- 1 file changed, 19 insertions(+), 23 deletions(-)
--- 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, st 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, st /* 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, st
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, st 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: IN/%s OUT/%s NOTIFY/%s\n", @@ -696,14 +700,6 @@ acm_bind(struct usb_configuration *c, st 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)