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CVE-2024-36894 Affecting kernel-uek-debug-devel package, versions <0:5.15.0-210.163.7.el8uek

Severity

 Recommended
high

Based on Oracle Linux security rating.

Threat Intelligence

EPSS
0.04% (15th percentile)

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  • Snyk IDSNYK-ORACLE8-KERNELUEKDEBUGDEVEL-7942130
  • published13 Sept 2024
  • disclosed30 May 2024
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Introduced: 30 May 2024

CVE-2024-36894  (opens in a new tab)

How to fix?

Upgrade Oracle:8 kernel-uek-debug-devel to version 0:5.15.0-210.163.7.el8uek or higher.
This issue was patched in ELSA-2024-12618.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-uek-debug-devel package and not the kernel-uek-debug-devel package as distributed by Oracle. See How to fix? for Oracle:8 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete

FFS based applications can utilize the aio_cancel() callback to dequeue pending USB requests submitted to the UDC. There is a scenario where the FFS application issues an AIO cancel call, while the UDC is handling a soft disconnect. For a DWC3 based implementation, the callstack looks like the following:

DWC3 Gadget                               FFS Application

dwc3_gadget_soft_disconnect() ... --> dwc3_stop_active_transfers() --> dwc3_gadget_giveback(-ESHUTDOWN) --> ffs_epfile_async_io_complete() ffs_aio_cancel() --> usb_ep_free_request() --> usb_ep_dequeue()

There is currently no locking implemented between the AIO completion handler and AIO cancel, so the issue occurs if the completion routine is running in parallel to an AIO cancel call coming from the FFS application. As the completion call frees the USB request (io_data->req) the FFS application is also referencing it for the usb_ep_dequeue() call. This can lead to accessing a stale/hanging pointer.

commit b566d38857fc ("usb: gadget: f_fs: use io_data->status consistently") relocated the usb_ep_free_request() into ffs_epfile_async_io_complete(). However, in order to properly implement locking to mitigate this issue, the spinlock can't be added to ffs_epfile_async_io_complete(), as usb_ep_dequeue() (if successfully dequeuing a USB request) will call the function driver's completion handler in the same context. Hence, leading into a deadlock.

Fix this issue by moving the usb_ep_free_request() back to ffs_user_copy_worker(), and ensuring that it explicitly sets io_data->req to NULL after freeing it within the ffs->eps_lock. This resolves the race condition above, as the ffs_aio_cancel() routine will not continue attempting to dequeue a request that has already been freed, or the ffs_user_copy_work() not freeing the USB request until the AIO cancel is done referencing it.

This fix depends on commit b566d38857fc ("usb: gadget: f_fs: use io_data->status consistently")

References

CVSS Scores

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