CVE-2026-90001
HighCVSS 7.8Summary
In the Linux kernel, a race condition exists in the HID BPF subsystem between the device destruction path (__hid_bpf_ops_destroy_device) and the unregistration path (hid_bpf_unreg), which can double-put the same device reference. This frees the hid_device structure while hid_destroy_device() is still using it, resulting in a use-after-free. The fix serializes the reference release decision under the prog_list_lock.
Risk Assessment
The vulnerability can lead to a use-after-free in the kernel, which on systems with HID BPF enabled may cause a kernel panic or potentially allow privilege escalation. Exploitation requires the ability to load BPF programs and interact with the HID subsystem, limiting the pool of potential attackers.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-90001. If updating is not possible, consider restricting the ability to load HID BPF programs to trusted users.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: HID: bpf: serialize device reference release in struct_ops destroy path __hid_bpf_ops_destroy_device() and hid_bpf_unreg() can race on the same registration reference, double-putting struct hid_device and freeing it while hid_destroy_device() still uses it. Serialize the remove/NULL decision under hdev->bpf.prog_list_lock 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 put_device() 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 (hid_bpf_ops_reg) acquires one device reference (hid_get_device()). Two paths can release it: - device destruction: hid_destroy_device() -> hid_bpf_destroy_device() -> __hid_bpf_ops_destroy_device(), which walks hdev->bpf.prog_list under rcu_read_lock() and drops one reference per attached program; - BPF link release: bpf map delete (no BPF_F_LINK) synchronously calls st_ops->unreg() -> hid_bpf_unreg(), 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 (rcu_read_lock vs prog_list_lock), so a concurrent unreg can read ops->hdev as non-NULL, block on prog_list_lock, 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 refcount_t saturation fires: the device is simply freed while the transport is still inside hid_destroy_device(), and subsequent teardown touches freed memory. The fix serializes the remove/NULL decision under prog_list_lock 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 READ_ONCE/WRITE_ONCE are added, keeping the patch minimal. Unlocked-read safety: the unlocked read of ops->hdev at the top of hid_bpf_unreg() cannot touch a freed device, because the unreg path itself still holds this registration's reference (released only by its own hid_put_device() 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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS