USB: gadget: dummy-hcd: Fix "task hung" problem
The syzbot fuzzer has been encountering "task hung" problems ever
since the dummy-hcd driver was changed to use hrtimers instead of
regular timers. It turns out that the problems are caused by a subtle
difference between the timer_pending() and hrtimer_active() APIs.
The changeover blindly replaced the first by the second. However,
timer_pending() returns True when the timer is queued but not when its
callback is running, whereas hrtimer_active() returns True when the
hrtimer is queued _or_ its callback is running. This difference
occasionally caused dummy_urb_enqueue() to think that the callback
routine had not yet started when in fact it was almost finished. As a
result the hrtimer was not restarted, which made it impossible for the
driver to dequeue later the URB that was just enqueued. This caused
usb_kill_urb() to hang, and things got worse from there.
Since hrtimers have no API for telling when they are queued and the
callback isn't running, the driver must keep track of this for itself.
That's what this patch does, adding a new "timer_pending" flag and
setting or clearing it at the appropriate times.
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Linux |
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Configuration 1 [-]
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No data.
No data.
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
Wed, 01 Oct 2025 21:15:00 +0000
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| Metrics |
ssvc
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Thu, 13 Feb 2025 00:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-824 |
Tue, 12 Nov 2024 15:15:00 +0000
| Type | Values Removed | Values Added |
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| First Time appeared |
Linux
Linux linux Kernel |
|
| Weaknesses | NVD-CWE-noinfo | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc3:*:*:*:*:*:* |
|
| Vendors & Products |
Linux
Linux linux Kernel |
Fri, 08 Nov 2024 16:15:00 +0000
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|---|---|---|
| References |
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Wed, 06 Nov 2024 13:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Tue, 05 Nov 2024 17:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: USB: gadget: dummy-hcd: Fix "task hung" problem The syzbot fuzzer has been encountering "task hung" problems ever since the dummy-hcd driver was changed to use hrtimers instead of regular timers. It turns out that the problems are caused by a subtle difference between the timer_pending() and hrtimer_active() APIs. The changeover blindly replaced the first by the second. However, timer_pending() returns True when the timer is queued but not when its callback is running, whereas hrtimer_active() returns True when the hrtimer is queued _or_ its callback is running. This difference occasionally caused dummy_urb_enqueue() to think that the callback routine had not yet started when in fact it was almost finished. As a result the hrtimer was not restarted, which made it impossible for the driver to dequeue later the URB that was just enqueued. This caused usb_kill_urb() to hang, and things got worse from there. Since hrtimers have no API for telling when they are queued and the callback isn't running, the driver must keep track of this for itself. That's what this patch does, adding a new "timer_pending" flag and setting or clearing it at the appropriate times. | |
| Title | USB: gadget: dummy-hcd: Fix "task hung" problem | |
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-10-01T20:27:18.736Z
Reserved: 2024-10-21T19:36:19.945Z
Link: CVE-2024-50100
Vulnrichment
Updated: 2025-10-01T15:14:49.082Z
NVD
Status : Modified
Published: 2024-11-05T18:15:13.757
Modified: 2025-10-01T21:15:46.963
Link: CVE-2024-50100
Redhat
OpenCVE Enrichment
No data.