Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: USB: dummy-hcd: Fix locking/synchronization error Syzbot testing was able to provoke an addressing exception and crash in the usb_gadget_udc_reset() routine in drivers/usb/gadgets/udc/core.c, resulting from the fact that the routine was called with a second ("driver") argument of NULL. The bad caller was set_link_state() in dummy_hcd.c, and the problem arose because of a race between a USB reset and driver unbind. These sorts of races were not supposed to be possible; commit 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change"), along with a few followup commits, was written specifically to prevent them. As it turns out, there are (at least) two errors remaining in the code. Another patch will address the second error; this one is concerned with the first. The error responsible for the syzbot crash occurred because the stop_activity() routine will sometimes drop and then re-acquire the dum->lock spinlock. A call to stop_activity() occurs in set_link_state() when handling an emulated USB reset, after the test of dum->ints_enabled and before the increment of dum->callback_usage. This allowed another thread (doing a driver unbind) to sneak in and grab the spinlock, and then clear dum->ints_enabled and dum->driver. Normally this other thread would have to wait for dum->callback_usage to go down to 0 before it would clear dum->driver, but in this case it didn't have to wait since dum->callback_usage had not yet been incremented. The fix is to increment dum->callback_usage _before_ calling stop_activity() instead of after. Then the thread doing the unbind will not clear dum->driver until after the call to usb_gadget_udc_reset() safely returns and dum->callback_usage has been decremented again.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 6350c7dd33ab481ef41c931a238361490c32d15c; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before cc97fb5969177cccce2e23b31298df220fc7570d; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 218886b2ef2dea7627d3700ab0abaf4bf9d1161f; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 791966f85b439b261bf19865cf1c07c065ffb4b4; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 805b1833d6ed6da5086e610578a28e71bb54fbbb; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before efbd9441f1e769a7aae1813d497cec09cbdff031; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 69ab97a693251d6a6093e630060a3c744fd58524; affected 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 before 616a63ff495df12863692ab3f9f7b84e3fa7a66d; affected 7b416b9dac6ede26d4ca0c1a88b448b543623ff3; affected 8590bc1da625dd4a589eac0fc3aa3cf4f400424d; affected a867d5b932ac4911d3f8a1e63505061b0c81f889; affected e84b4a008365b7edbd842a063ae28d040a98db25; affected e39b17143a5b5aac81f066d455e5d3a9877eb3ae; affected 4f8ae1fcb0dfbb72a7678f81bf01fb7fc85c6715; affected 3.2.97 before 3.3; affected 3.16.52 before 3.17; affected 4.1.46 before 4.2; affected 4.4.92 before 4.5; affected 4.9.55 before 4.10; affected 4.13.6 before 4.14 |
| Linux / Linux | affected 4.14; unaffected 0 before 4.14; unaffected 5.10.253 through 5.10.*; unaffected 5.15.203 through 5.15.*; unaffected 6.1.168 through 6.1.*; unaffected 6.6.134 through 6.6.*; unaffected 6.12.81 through 6.12.*; unaffected 6.18.22 through 6.18.*; unaffected 6.19.12 through 6.19.*; unaffected 7.0 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c
- https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d
- https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f
- https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4
- https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb
- https://git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031
- https://git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524
- https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d