UBUNTU-CVE-2024-50100
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.
02 / AFFECTED SOFTWARE
Affected packages
16 explicit affected versions
29 explicit affected versions
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26 explicit affected versions
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10 explicit affected versions
10 explicit affected versions
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37 explicit affected versions
8 explicit affected versions
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51 explicit affected versions
13 explicit affected versions
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23 explicit affected versions
7 explicit affected versions
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26 explicit affected versions
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4 explicit affected versions
4 explicit affected versions
16 explicit affected versions
9 explicit affected versions
12 explicit affected versions
13 explicit affected versions
7 explicit affected versions
13 explicit affected versions
7 explicit affected versions
10 explicit affected versions
14 explicit affected versions
50 explicit affected versions
18 explicit affected versions
3 explicit affected versions
16 explicit affected versions
43 explicit affected versions
11 explicit affected versions
11 explicit affected versions
35 explicit affected versions
12 explicit affected versions
13 explicit affected versions
6 explicit affected versions
12 explicit affected versions
12 explicit affected versions
27 explicit affected versions
12 explicit affected versions
7 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/5189df7b8088268012882c220d6aca4e64981348
- https://git.kernel.org/stable/c/5189df7b8088268012882c220d6aca4e64981348
- https://git.kernel.org/stable/c/f828205ee3e4ddc712a13fba6c9902d51e91ddaf
- https://ubuntu.com/security/CVE-2024-50100
- https://ubuntu.com/security/notices/USN-7276-1
- https://ubuntu.com/security/notices/USN-7277-1
- https://ubuntu.com/security/notices/USN-7310-1
- https://www.cve.org/CVERecord?id=CVE-2024-50100