CVE-2026-80778
Dashboard / Vulnerabilities / CVE-2026-80778
Summary: futex/pi: Reject cross-mm private futex owners
Details: In the Linux kernel, the following vulnerability has been resolved: futex/pi: Reject cross-mm private futex owners A private futex key borrows the waiter's mm without taking an mm_users reference. Nevertheless, attach_to_pi_owner() currently accepts an owner from a different address space and copies the private key into the owner's PI state. When that owner exits, exit_pi_state_list() uses the saved key to find the hash bucket and acquires a reference to the waiter's private hash. If the last user of the waiter's mm exits concurrently, futex_hash_free() frees the hash while the owner still uses its bucket and reference. Prevent this by validating in attach_to_pi_owner() that, for private futexes, the owner mm and waiter mm are the same. Perform the check with the owner's pi_lock held and after validating owner::futex::state to serialize against a concurrent PI-state exit cleanup. [ tglx: Amended comment ]
References: https://git.kernel.org/stable/c/2b92e5562653b5293529f63b0300837d9dcedbd7, https://git.kernel.org/stable/c/43b148d796aa338858792d0167cebdc12b8cb4b9, https://git.kernel.org/stable/c/59b3732f95dda1fbd2234514d35f4fb6b5bb6d85, https://git.kernel.org/stable/c/f7fb3e07752688842cbe0b85cf0d98c2fbf76b68, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80778.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80778, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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