UBUNTU-CVE-2026-90001: High severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: HID: bpf: serialize device reference release in structops destroy path hidbpfopsdestroydevice() and hidbpfunreg() can race on the same registration reference, double-putting struct hiddevice and freeing it while hiddestroydevice() still uses it. Serialize the remove/NULL decision under hdev->bpf.proglistlock so exactly one path releases each registration reference: unreg re-checks ops->hdev under the lock and returns without putting when the destroy path already cleared it; all putdevice() calls happen after the lock is dropped, which is safe because a concurrent unreg then observes ops->hdev == NULL under the lock. Background: each successful attach (hidbpfopsreg) acquires one device reference (hidgetdevice()). Two paths can release it: - device destruction: hiddestroydevice() -> hidbpfdestroydevice() -> hidbpfopsdestroydevice(), which walks hdev->bpf.proglist under rcureadlock() and drops one reference per attached program; - BPF link release: bpf map delete (no BPFFLINK) synchronously calls stops->unreg() -> hidbpfunreg(), which drops the reference for its own registration. The coordination handshake (e->hdev = NULL on the destroy side vs "if (!hdev) return" on the unreg side) is a TOCTOU check: the two paths run under different lock domains (rcureadlock vs proglistlock), so a concurrent unreg can read ops->hdev as non-NULL, block on proglistlock, and then proceed while the destroy traversal executes - both paths then drop the same reference. The refcount reaches zero legitimately (each decrement is individually valid), so no refcountt saturation fires: the device is simply freed while the transport is still inside hiddestroydevice(), and subsequent teardown touches freed memory. The fix serializes the remove/NULL decision under proglistlock on both sides and moves the destroy-side puts outside the lock. With the lock held, plain reads/writes of ops->hdev are sufficient; no READONCE/WRITEONCE are added, keeping the patch minimal. Unlocked-read safety: the unlocked read of ops->hdev at the top of hidbpfunreg() cannot touch a freed device, because the unreg path itself still holds this registration's reference (released only by its own hidputdevice() after the lock is dropped), and a destroy traversal that already cleared ops->hdev makes the lock-internal re-check return early without any put. At most one of the two paths releases each registration reference.