CVE-2026-80778
futex/pi: Reject cross-mm private futex owners
Description
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 ]
INFO
Published Date :
Sept. 4, 2026, 4:18 p.m.
Last Modified :
Sept. 4, 2026, 4:18 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Validate owner and waiter memory managers are identical for private futexes.
- Acquire owner's pi_lock before validation.
- Check owner::futex::state for serialization.
- Apply updates provided by the vendor.
References to Advisories, Solutions, and Tools
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CVE-2026-80778.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-80778 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-80778
weaknesses.
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 04, 2026
Action Type Old Value New Value Added Description 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 ] Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/80xxx/CVE-2026-80778.json">CVE-2026-80778</a> Added Reference https://git.kernel.org/stable/c/2b92e5562653b5293529f63b0300837d9dcedbd7 Added Reference https://git.kernel.org/stable/c/43b148d796aa338858792d0167cebdc12b8cb4b9 Added Reference https://git.kernel.org/stable/c/59b3732f95dda1fbd2234514d35f4fb6b5bb6d85 Added Reference https://git.kernel.org/stable/c/f7fb3e07752688842cbe0b85cf0d98c2fbf76b68