CVE-2026-89881: media: rtl2832_sdr: use vb2_video_unregister_device() on remove to fix DMA leak
In the Linux kernel, the following vulnerability has been resolved:
media: rtl2832sdr: use vb2videounregisterdevice() on remove to fix DMA leak
rtl2832sdrremove() runs on USB disconnect and clears dev->udev to NULL before any pending streaming teardown has run. When user space later closes its file descriptor, vb2 calls rtl2832sdrstopstreaming() which in turn calls rtl2832sdrfreestreambufs(). That helper releases each coherent buffer with:
usbfreecoherent(dev->udev, dev->bufsize, dev->buflist[dev->bufnum], dev->dmaaddr[dev->bufnum]);
usbfreecoherent() returns immediately when its dev argument is NULL, so every DMA stream buffer that was live at disconnect is silently leaked. The URBs allocated in rtl2832sdrallocurbs() outlive the device for the same reason.
The rtl2832sdr driver uses vb2foprelease() in its fileoperations, so replace videounregisterdevice(&dev->vdev) with vb2videounregisterdevice(&dev->vdev) and move it before clearing dev->udev. vb2videounregisterdevice() releases the vb2 queue, which synchronously runs rtl2832sdrstopstreaming() if streaming is active, so URBs and coherent DMA stream buffers are freed while dev->udev is still valid.
vb2videounregisterdevice() locks vdev->queue->lock (vbqueuelock) internally, and stopstreaming() locks v4l2lock, so the previous outer mutexlock(&dev->vbqueuelock) / mutexlock(&dev->v4l2lock) pair around the unregister sequence would self-deadlock and has been removed. A short v4l2lock critical section around dev->udev = NULL remains so any ioctl path that still holds the file descriptor sees coherent state.
Issue identified by automated review of the INV-003 series at https://sashiko.dev/
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Fixed in 6.6.157.1-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Upgrade
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1119.126~20.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-202.212 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1125.134 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1119.126+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-202.212+fips1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
When does the leak occur?
It occurs when an rtl2832_sdr USB device disconnects while DMA streaming resources are still live. The affected path is triggered when streaming teardown is deferred until user space closes its file descriptor after the disconnect.
What conditions are required to trigger it?
An rtl2832_sdr device must be in use with allocated streaming buffers or URBs, then disconnect before pending streaming teardown completes. The file descriptor can remain open at disconnect and be closed later, causing cleanup to run after the USB device pointer has been cleared.
How can I tell whether a system may have encountered the issue?
Systems are relevant if they use the rtl2832_sdr driver and a USB disconnect occurred during active SDR streaming or before the application closed its device file descriptor. In that scenario, coherent DMA stream buffers and URBs allocated for the stream may remain leaked.