CVE-2025-68194
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-12-16

Last updated on: 2025-12-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: media: imon: make send_packet() more robust syzbot is reporting that imon has three problems which result in hung tasks due to forever holding device lock [1]. First problem is that when usb_rx_callback_intf0() once got -EPROTO error after ictx->dev_present_intf0 became true, usb_rx_callback_intf0() resubmits urb after printk(), and resubmitted urb causes usb_rx_callback_intf0() to again get -EPROTO error. This results in printk() flooding (RCU stalls). Alan Stern commented [2] that In theory it's okay to resubmit _if_ the driver has a robust error-recovery scheme (such as giving up after some fixed limit on the number of errors or after some fixed time has elapsed, perhaps with a time delay to prevent a flood of errors). Most drivers don't bother to do this; they simply give up right away. This makes them more vulnerable to short-term noise interference during USB transfers, but in reality such interference is quite rare. There's nothing really wrong with giving up right away. but imon has a poor error-recovery scheme which just retries forever; this behavior should be fixed. Since I'm not sure whether it is safe for imon users to give up upon any error code, this patch takes care of only union of error codes chosen from modules in drivers/media/rc/ directory which handle -EPROTO error (i.e. ir_toy, mceusb and igorplugusb). Second problem is that when usb_rx_callback_intf0() once got -EPROTO error before ictx->dev_present_intf0 becomes true, usb_rx_callback_intf0() always resubmits urb due to commit 8791d63af0cf ("[media] imon: don't wedge hardware after early callbacks"). Move the ictx->dev_present_intf0 test introduced by commit 6f6b90c9231a ("[media] imon: don't parse scancodes until intf configured") to immediately before imon_incoming_packet(), or the first problem explained above happens without printk() flooding (i.e. hung task). Third problem is that when usb_rx_callback_intf0() is not called for some reason (e.g. flaky hardware; the reproducer for this problem sometimes prevents usb_rx_callback_intf0() from being called), wait_for_completion_interruptible() in send_packet() never returns (i.e. hung task). As a workaround for such situation, change send_packet() to wait for completion with timeout of 10 seconds.
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Meta Information
Published
2025-12-16
Last Modified
2025-12-18
Generated
2026-05-06
AI Q&A
2025-12-16
EPSS Evaluated
2026-05-05
NVD
CVE-2025-68194
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
media imon *
linux kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability in the Linux kernel's imon media driver involves three main problems causing hung tasks by indefinitely holding a device lock. First, the usb_rx_callback_intf0() function repeatedly resubmits USB requests (URBs) upon receiving a -EPROTO error without a robust error-recovery scheme, leading to continuous retries and printk() flooding (RCU stalls). Second, the function resubmits URBs even before the device interface is fully present, causing hung tasks without flooding. Third, if usb_rx_callback_intf0() is not called (due to flaky hardware), the send_packet() function waits indefinitely for completion, causing hung tasks. The patch fixes these by improving error handling, adjusting checks for device presence, and adding a timeout to send_packet()'s wait.


How can this vulnerability impact me? :

This vulnerability can cause the system to experience hung tasks due to the imon driver indefinitely holding device locks. This can lead to system instability, degraded performance, or unresponsiveness, especially in scenarios involving USB media devices using the imon driver. The continuous retries and printk() flooding can also cause resource exhaustion and potential system stalls.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where the imon driver has been patched to fix the issues causing hung tasks and infinite retries. The patch improves error recovery by limiting retries on -EPROTO errors, moves device presence checks to prevent hung tasks, and adds a timeout to send_packet() to avoid indefinite waits. Until the patch is applied, consider monitoring for hung tasks related to the imon driver and avoid using affected hardware if possible.


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