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Jimmy Hu
7a5214dae9
commit 67e511d298 upstream.
The udc structure acts as the management structure for the gadget,
but their lifecycles are decoupled. A race condition exists where
usb_del_gadget() frees the udc memory (e.g., via mode-switch work)
while gadget_match_driver() concurrently accesses the freed udc memory
(e.g., via configfs), causing a Use-After-Free (UAF) that triggers a
NULL pointer dereference when the freed memory is zeroed:
[39430.908615][ T1171] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[39430.911397][ T1171] pc : __pi_strcmp+0x20/0x140
[39430.911441][ T1171] lr : gadget_match_driver+0x34/0x60
...
[39430.911890][ T1171] usb_gadget_register_driver_owner+0x50/0xf8
[39430.911910][ T1171] gadget_dev_desc_UDC_store+0xf4/0x140
[39430.931308][ T1171] configfs_write_iter+0xec/0x134
[39430.957058][ T1171] Workqueue: events_freezable __dwc3_set_mode
[39430.957287][ T1171] dwc3_gadget_exit+0x34/0x8c
[39430.957304][ T1171] __dwc3_set_mode+0xc0/0x664
Fix this by ensuring the udc structure remains allocated until the
gadget is released. To achieve this, introduce a new
usb_gadget_release() routine to the core. When the gadget is added,
usb_add_gadget() stores the gadget's release routine in the udc
structure and takes a reference to the udc. When the gadget is
released, usb_gadget_release() drops the reference to the udc and
then calls the gadget's release routine.
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: Jimmy Hu <hhhuuu@google.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://patch.msgid.link/20260625073705.803880-1-hhhuuu@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.