{"id":"CVE-2026-43327","summary":"USB: dummy-hcd: Fix locking/synchronization error","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nUSB: dummy-hcd: Fix locking/synchronization error\n\nSyzbot testing was able to provoke an addressing exception and crash\nin the usb_gadget_udc_reset() routine in\ndrivers/usb/gadgets/udc/core.c, resulting from the fact that the\nroutine was called with a second (\"driver\") argument of NULL.  The bad\ncaller was set_link_state() in dummy_hcd.c, and the problem arose\nbecause of a race between a USB reset and driver unbind.\n\nThese sorts of races were not supposed to be possible; commit\n7dbd8f4cabd9 (\"USB: dummy-hcd: Fix erroneous synchronization change\"),\nalong with a few followup commits, was written specifically to prevent\nthem.  As it turns out, there are (at least) two errors remaining in\nthe code.  Another patch will address the second error; this one is\nconcerned with the first.\n\nThe error responsible for the syzbot crash occurred because the\nstop_activity() routine will sometimes drop and then re-acquire the\ndum-\u003elock spinlock.  A call to stop_activity() occurs in\nset_link_state() when handling an emulated USB reset, after the test\nof dum-\u003eints_enabled and before the increment of dum-\u003ecallback_usage.\nThis allowed another thread (doing a driver unbind) to sneak in and\ngrab the spinlock, and then clear dum-\u003eints_enabled and dum-\u003edriver.\nNormally this other thread would have to wait for dum-\u003ecallback_usage\nto go down to 0 before it would clear dum-\u003edriver, but in this case it\ndidn't have to wait since dum-\u003ecallback_usage had not yet been\nincremented.\n\nThe fix is to increment dum-\u003ecallback_usage _before_ calling\nstop_activity() instead of after.  Then the thread doing the unbind\nwill not clear dum-\u003edriver until after the call to\nusb_gadget_udc_reset() safely returns and dum-\u003ecallback_usage has been\ndecremented again.","modified":"2026-07-15T01:49:06.807289106Z","published":"2026-05-08T13:31:12.896Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43327.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524"},{"type":"WEB","url":"https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43327.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43327"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7dbd8f4cabd96db5a50513de9d83a8105a5ffc81"},{"fixed":"6350c7dd33ab481ef41c931a238361490c32d15c"},{"fixed":"cc97fb5969177cccce2e23b31298df220fc7570d"},{"fixed":"218886b2ef2dea7627d3700ab0abaf4bf9d1161f"},{"fixed":"791966f85b439b261bf19865cf1c07c065ffb4b4"},{"fixed":"805b1833d6ed6da5086e610578a28e71bb54fbbb"},{"fixed":"efbd9441f1e769a7aae1813d497cec09cbdff031"},{"fixed":"69ab97a693251d6a6093e630060a3c744fd58524"},{"fixed":"616a63ff495df12863692ab3f9f7b84e3fa7a66d"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"7b416b9dac6ede26d4ca0c1a88b448b543623ff3"},{"last_affected":"8590bc1da625dd4a589eac0fc3aa3cf4f400424d"},{"last_affected":"a867d5b932ac4911d3f8a1e63505061b0c81f889"},{"last_affected":"e84b4a008365b7edbd842a063ae28d040a98db25"},{"last_affected":"e39b17143a5b5aac81f066d455e5d3a9877eb3ae"},{"last_affected":"4f8ae1fcb0dfbb72a7678f81bf01fb7fc85c6715"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.2.97"},{"fixed":"3.3"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.16.52"},{"fixed":"3.17"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.1.46"},{"fixed":"4.2"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.4.92"},{"fixed":"4.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.9.55"},{"fixed":"4.10"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.13.6"},{"fixed":"4.14"}]}],"versions":["v3.16.51","v3.2.96","v3.2.95","v3.16.50","v4.13","v3.2.94","v3.16.49","v4.1.45","v3.16.48","v3.2.93","v4.13.5","v4.9.54","v4.4.91","v4.9.53","v4.4.90","v4.13.4","v4.9.52","v4.4.89","v4.1.44","v4.13.3","v4.9.51","v4.4.88","v4.13-rc2","v4.13.2","v4.9.50","v3.2.92","v3.16.47","v4.13.1","v4.9.49","v4.4.87","v4.9.48","v4.13-rc1","v4.13-rc3","v4.9.47","v4.4.86","v4.13-rc7","v4.9.46","v4.4.85","v4.1.43","v4.13-rc4","v4.13-rc5","v4.13-rc6","v4.9.45","v4.4.84","v3.16.46","v3.2.91","v4.9.44","v4.4.83","v4.9.43","v4.4.82","v4.9.42","v4.4.81","v4.4.80","v4.9.41","v4.4.79","v4.9.40","v4.12-rc1","v4.9.39","v4.4.78","v4.1.42","v4.12","v4.4.77","v4.9.38","v3.16.45","v3.2.90","v4.9.37","v4.4.76","v4.12-rc5","v4.9.36","v4.12-rc7","v4.9.35","v4.4.75","v3.16.44","v3.2.89","v4.12-rc6","v4.12-rc4","v4.9.34","v4.4.74","v4.12-rc2","v4.4.73","v4.1.41","v4.9.33","v4.12-rc3","v4.9.32","v4.4.72","v4.11","v4.9.31","v4.4.71","v4.1.40","v4.9.30","v4.4.70","v3.16.43","v3.2.88","v4.9.29","v4.4.69","v4.9.28","v4.4.68","v4.1.39","v4.9.27","v4.4.67","v4.11-rc1","v4.9.26","v4.4.66","v4.11-rc6","v4.9.25","v4.4.65","v4.11-rc8","v4.4.64","v4.9.24","v4.4.63","v4.11-rc7","v4.11-rc3","v4.9.23","v4.4.62","v4.11-rc5","v4.11-rc2","v4.4.61","v4.9.22","v4.11-rc4","v4.9.21","v4.4.60","v4.4.59","v4.9.20","v3.16.42","v3.2.87","v4.9.19","v4.4.58","v4.9.18","v4.4.57","v4.10","v4.9.17","v4.4.56","v4.9.16","v4.4.55","v4.9.15","v4.4.54","v3.16.41","v3.2.86","v4.9.14","v4.4.53","v4.9.13","v4.4.52","v4.1.38","v4.9","v3.16.40","v3.2.85","v4.9.12","v4.4.51","v4.9.11","v4.4.50","v3.16.39","v3.2.84","v4.10-rc8","v4.10-rc3","v4.10-rc1","v4.10-rc7","v4.4.49","v4.9.10","v4.10-rc6","v4.10-rc2","v4.9.9","v4.4.48","v4.10-rc5","v4.9.8","v4.4.47","v4.9.7","v4.4.46","v4.9.6","v4.4.4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