{"id":"CVE-2026-68370","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-68370","summary":"usb: gadget: dummy_hcd: prevent fifo_req reuse during giveback","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: dummy_hcd: prevent fifo_req reuse during giveback\n\ndummy_hcd embeds a single shared usb_request (dum->fifo_req) that the\n\"emulated single-request FIFO\" fast-path in dummy_queue() reuses for\nsmall IN transfers: it copies the caller's request into it\n(req->req = *_req) and queues it, treating list_empty(&fifo_req.queue)\nas \"the slot is free\".\n\nThe completion side (dummy_timer/transfer/nuke/dummy_dequeue) follows\nthe standard pattern: list_del_init(&req->queue) unlinks the request,\nthen the lock is dropped and usb_gadget_giveback_request() invokes\nreq->complete().  But list_del_init() makes fifo_req.queue look empty\n*before* the completion callback returns, so a concurrent dummy_queue()\non another CPU sees the slot as free, reuses fifo_req and runs\nreq->req = *_req -- overwriting req->complete while dummy_timer is\nmid-calling it.  The indirect call then jumps to a clobbered pointer,\ncausing a general protection fault / page fault in dummy_timer\n(syzkaller extid faf3a6cf579fc65591ca).  The clobbering write is an\nin-bounds memcpy on a live shared object, so KASAN cannot flag it.\n\nAdd a fifo_req_busy bit covering the shared request's whole lifetime:\nset it in dummy_queue() when the FIFO fast-path takes fifo_req (making\nit the fast-path guard, replacing the list_empty(&fifo_req.queue)\ntest), and clear it after the completion callback has returned, via a\ndummy_giveback() helper used at all four gadget-request giveback\nsites.  The shared slot can no longer be reused until its completion\ncallback has finished.","published":"2026-08-10T12:03:48.320Z","modified":"2026-08-14T04:04:11.995610586Z","cvss":{"score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.6.148"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/67b589d09a96882d56842dced5698ed8dd06ce45"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d5e5cd3654d2b5359a12ea6586120f05b28634ee"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e239ea91b48180ed48a86ac25643832a02c88456"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e24b33618231034bf01dfaff4fd3409d4b4d5b2e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e2b2740f1242bc70b5b46da2cdbbaa419f490e59"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68370.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68370"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-14T04:04:11.995610586Z"}}