From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5C1B46D552 for ; Fri, 4 Sep 2026 15:14:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788534884; cv=none; b=M4qEjQkdveVn6jNQoT03Xrf63BZasQaZq3Xl1k4+oD56A05CRzD2aD46LgJzM4L6p5DGZ6JEXA8vKSy0oRGE7VCogCXGWPvRBDtPvUE7OB8XuRGDNxbTDGrw01vvkTUO8oW8fYMebD3Z/TfK6XKnxG4IleCz84l0I3o7BlsH8kw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788534884; c=relaxed/simple; bh=/mI0zEI3zZQPwESlzOyujAIMr7edC7H/ofIQATHKtiA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=e702i4p0wE83ATNqM/1bBu/JIS+5dtS5AI2Z80Qa4HoJlSOsESryl7JQit5lHzTO4yZOevW7bYwR2FtRblOtveKQvoYn0UQRoXN//ocjGBaYgJ4BIJITeBU/u+L+I6v2Pa6B8AiWdUiZ0CksnDzg82O37V2vVJhvUzKsVEmz94k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YqbSJolF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="YqbSJolF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88C931F00A3D; Fri, 4 Sep 2026 15:14:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788534882; bh=DG5vg9QA3LKqVuSjcv67A91LDhtAIEIBHxlc8+T5J/M=; h=From:To:Cc:Subject:Date:Reply-To; b=YqbSJolFK9/mhoQQbovdWXjj6jKZ5x01w5A8bTS2g/HJhrHcFiCNH5dI3u2IoKBGT rlxV1FkSZ7EV6GNReO3a7pBhX8hm5ZFamiamAL4yrpVtLvRkh9bCuPj8PYiwNWvzQ5 /KqFEJaFELBityQRdQQARt4LW4jHHpHGT0ZtNNrU= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80776: futex: Fix race in futex_pivot_pending() during private hash resize Date: Fri, 4 Sep 2026 17:11:15 +0200 Message-ID: <2026090403-CVE-2026-80776-d5ad@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4130; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=nZ5rGlUiwkaZyxxxjs4XQd8aLORJ5VkSeX68NGYbtCw=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmz7rfPvPfO/MW/guAbbA3/+yeeFAr5uv/Sy+wv+6c0T S34wt+6ryOWhUGQiUFWTJHlyzaeo/srDil6GdqehpnDygQyhIGLUwAmMk+QYcHGRRUHdhvw2yRu bg/5adrg17nvvR/DfK/ilu13A53iXeQlF9qveSkX84GhCwA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: futex: Fix race in futex_pivot_pending() during private hash resize A task performing a custom private hash resize can remain blocked in uninterruptible sleep indefinitely. The hung-task detector reports: INFO: task futex-resizer:314 blocked for more than 10 seconds. task:futex-resizer state:D stack:14824 pid:314 tgid:312 ppid:311 Call Trace: __schedule+0x521/0xf30 schedule+0x22/0xa0 futex_hash_allocate+0x3db/0x490 __do_sys_prctl+0x6f5/0xbd0 do_syscall_64+0xf9/0x530 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: hung_task: blocked tasks futex_pivot_pending() allows the resize request to continue when either no replacement hash is pending (hash_new == NULL) or the current hash reference count has reached zero. After the final-reference wake, another futex task can complete the pivot between the two observations: T1 T2 futex_hash_allocate() wait_var_event(mm, ...) futex_pivot_pending(mm) hash_new != NULL futex_hash() futex_ref_get(old) -> false futex_pivot_hash(mm) hash_new = NULL __futex_pivot_hash(mm, new) rcu_assign_pointer(hash, new) fph = rcu_dereference(hash) /* new */ futex_ref_is_dead(fph) -> false schedule() The pivot changes the state from hash_new != NULL with a dead current hash to hash_new == NULL with a live current hash. Because futex_pivot_pending() reads hash_new and hash without serialization, the resize task can observe hash_new in the pre-pivot state and hash in the post-pivot state, causing futex_pivot_pending() to return false even though the pivot has completed. The task then goes to sleep after the wakeup has already been consumed. Serialize state reads in futex_pivot_pending() using futex_mm_phash::lock. This guarantees that futex_pivot_pending() observes hash_new and hash atomically, eliminating the race condition. The Linux kernel CVE team has assigned CVE-2026-80776 to this issue. Affected and fixed versions =========================== Issue introduced in 6.16 with commit bd54df5ea7cadac520e346d5f0fe5d58e635b6ba and fixed in 6.18.46 with commit 4a7e941ca29a608c6244cbd028d3599ecaef7207 Issue introduced in 6.16 with commit bd54df5ea7cadac520e346d5f0fe5d58e635b6ba and fixed in 7.1.11 with commit 19b4be0717fa83265d66aea836b7022d898422cf Issue introduced in 6.16 with commit bd54df5ea7cadac520e346d5f0fe5d58e635b6ba and fixed in 7.2 with commit 8e7ff730dd96519a333d1570edf1c3fabb6d3629 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-80776 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: kernel/futex/core.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/4a7e941ca29a608c6244cbd028d3599ecaef7207 https://git.kernel.org/stable/c/19b4be0717fa83265d66aea836b7022d898422cf https://git.kernel.org/stable/c/8e7ff730dd96519a333d1570edf1c3fabb6d3629