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d96209626a
This patch follows up Zheng Wang's 2023 report of a use-after-free in
vudc_remove(). The original thread stalled on Shuah Khan's request for
runtime testing of the unplug/unbind path. This patch supplies that
testing and keeps Zheng's original fix shape.
In vudc_probe(), v_init_timer() binds udc->tr_timer.timer to v_timer().
usbip_sockfd_store() starts the timer via v_start_timer()/v_kick_timer().
vudc_remove() can then free the containing struct vudc while the timer is
still pending or executing.
KASAN confirms the race on an unpatched x86_64 QEMU guest with
CONFIG_KASAN=y, CONFIG_USBIP_VUDC=y, CONFIG_USB_ZERO=y, and a tight loop
that repeatedly writes a socket fd to usbip_sockfd, closes the socket
pair, and unbinds/rebinds usbip-vudc.0:
BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x8ba/0x8e0
Write of size 8 at addr ffff888001b80740 by task trigger_and_unb/239
Allocated by task 239:
vudc_probe+0x4d/0xaa0
Freed by task 239:
kfree+0x18f/0x520
device_release_driver_internal+0x388/0x540
unbind_store+0xd9/0x100
This lands in the timer core rather than v_timer() itself because the
embedded timer_list is being walked after its containing struct vudc has
already been freed. The underlying lifetime bug is the same one Zheng
reported.
With v_stop_timer() called from vudc_remove() and the timer deleted
synchronously, the same harness completed 5000 bind/unbind iterations
with no KASAN report.
Fixes:
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History
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|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| stub.h | ||
| stub_dev.c | ||
| stub_main.c | ||
| stub_rx.c | ||
| stub_tx.c | ||
| usbip_common.c | ||
| usbip_common.h | ||
| usbip_event.c | ||
| vhci.h | ||
| vhci_hcd.c | ||
| vhci_rx.c | ||
| vhci_sysfs.c | ||
| vhci_tx.c | ||
| vudc.h | ||
| vudc_dev.c | ||
| vudc_main.c | ||
| vudc_rx.c | ||
| vudc_sysfs.c | ||
| vudc_transfer.c | ||
| vudc_tx.c | ||