Bug 2395287 (CVE-2023-53219)

Summary: CVE-2023-53219 kernel: media: netup_unidvb: fix use-after-free at del_timer()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-09-15 15:05:29 UTC
In the Linux kernel, the following vulnerability has been resolved:

media: netup_unidvb: fix use-after-free at del_timer()

When Universal DVB card is detaching, netup_unidvb_dma_fini()
uses del_timer() to stop dma->timeout timer. But when timer
handler netup_unidvb_dma_timeout() is running, del_timer()
could not stop it. As a result, the use-after-free bug could
happen. The process is shown below:

    (cleanup routine)          |        (timer routine)
                               | mod_timer(&dev->tx_sim_timer, ..)
netup_unidvb_finidev()         | (wait a time)
  netup_unidvb_dma_fini()      | netup_unidvb_dma_timeout()
    del_timer(&dma->timeout);  |
                               |   ndev->pci_dev->dev //USE

Fix by changing del_timer() to del_timer_sync().