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Sam Day 1226293ec9 usbip: vudc: fix NULL deref in vep_dequeue() 
commit c5371e0b91 upstream.

vep_alloc_request() wasn't initializing vrequest->udc, so cancellations
on the FunctionFS AIO path were arriving in vep_dequeue without a valid
UDC reference.

Since vrequest->udc is never actually properly used anywhere, we opt to
remove it, and update vep_dequeue to obtain a reference to the udc with
ep_to_vudc(), consistent with the other vep_ ops.

AFAICT this bug has existed for ~10 years. Seems that nobody has really
stressed the FunctionFS AIO path on usbip's vudc.

I tested this fix in a QEMU aarch64 guest driving FunctionFS endpoints
via AIO. Before the fix, running `usbip attach` from the host would
cause the guest to oops with the following backtrace:

Call trace:
 vep_dequeue+0x1c/0xe4 (P)
 usb_ep_dequeue+0x14/0x20
 ffs_aio_cancel+0x24/0x34
 __arm64_sys_io_cancel+0xb0/0x124
 do_el0_svc+0x68/0x100
 el0_svc+0x18/0x5c
 el0t_64_sync_handler+0x98/0xdc
 el0t_64_sync+0x154/0x158

Assisted-by: opencode:openai/gpt-5.5
Cc: stable <stable@kernel.org>
Fixes: b6a0ca1118 ("usbip: vudc: Add UDC specific ops")
Reviewed-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: Sam Day <me@samcday.com>
Link: https://patch.msgid.link/20260626-usbip-vudc-deque-fix-v3-1-98c2dc4d6a48@samcday.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-07-24 15:51:24 +02:00
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README 

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.