From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32D3F12F5A5 for ; Tue, 2 Dec 2025 02:03:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764641018; cv=none; b=rnaW7YawN56DARTVG3PKA39dbzf9dvT7bNT00nvtttBmdaDTgJBiebzRTilNyv/EfGAUh5zSpfd6hvqS0LOPl7EcEkNIsewrRhul1zE2BcOij/QmwYi8HNZQfAf2k3ONQ+uJ7JAdrvWpq3iB1jz+35a3qjqfrNzdoqOzfKFKw4E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764641018; c=relaxed/simple; bh=8rVJ83FzmRhqZVUzcIEknO74P8qXDaJF37XTfxZBEtQ=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=ShntH2SWk3pb76GpGD7Of4vYcZG+hnBjXIxlRGlxvajvxm+I0TkTZ5+Q2UtUZUZiKPq5342PpO6KsTKWVtlywWirtPFkELaHfDiEdSL6uSqqQJ1hPorrniyyitst19NaZ/kqAcDtuTIXWpne0ybNWmHrB/dnWbNbf1v91uRieFs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=hym4x8nl; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="hym4x8nl" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-29846a9efa5so90424095ad.0 for ; Mon, 01 Dec 2025 18:03:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1764641016; x=1765245816; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=saqGmG+fZVbqKzI/92Gz3sReZk08mzLEAomu2owol5w=; b=hym4x8nlsv5inu+PMp8yQMHPEXGImMikc8K0UzD2NUKqZpZiq5u2AtyenWwMmkvQM+ AJyQCtDpnz555fRAcxYWiU7W9hujCvWyW8UHyRKOaNcIgZdnmGazfr6WpqZ3qZEsjzgG xnQRmChehT54mOooa/uSJoDv2/u/SeS/u1/yTRjAqndjzaFBwXC+L1kkuXcitSTzdVip XQLY+u1oxvgBrDtfVqXsz2048EJYrEbs9Q2Ga3Hl1G2Pl1GJwPZnlB+lYgrdWFq+/2me dJExdA03fctyhHtePgG6GgiVkoozPw5Q00FcEDMDbL1uA/Sscf0fZE/yLe0RMMlDfqvj ybiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764641016; x=1765245816; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=saqGmG+fZVbqKzI/92Gz3sReZk08mzLEAomu2owol5w=; b=E6DNUrHJ3bcvy3dV/kl/Jvhau/12Zn6Sn7lkD7E26PTT0yD6dhiTJJKsESwbbPs5Zp uukDeMz4slDUba4cl3gVSlIbOfCGNVg44W0WhXM+aVnHZpXiBZ82/XCsXr4VXL8FiCDC YN6rhAEwqiAecCAh5r4y7WayGNHwMS3r/iME/AZKIq95CFkg24t2ZRz/cLU2BHiYbPjU KOJX9gBnOueQ/ziPj8qA/25OembFyUbTS86ocOPeuFIuTQ9E+6pRg/34l29ngNNbLXvH +egY7SnkXqLvW6tleU3523+g83Ppj55sNqmc/THLrIWiruE4WCYD4bCzWc9z/C0kaqSX wDRQ== X-Forwarded-Encrypted: i=1; AJvYcCVkO/jkUnZc8+7CXLy7ygLjo3dSRme61j5Cx54MRI6oJTxW3wKiCJ4g8ahp9bIWFOr6iH66rnHGTHMFEg4=@vger.kernel.org X-Gm-Message-State: AOJu0Ywb6/OvbOCoW1zJ9VzPrbzYB3gmERnm3+DNnzCXiCgIjU6BkTp6 G5gs+KPVbRBPl3VOHYKNvAwHU1+ojwA3RxvmKIx7WrI5Y4bskYWo+wfnRe0R8KzIbjkGT1cF1kB VvSastg== X-Google-Smtp-Source: AGHT+IHgSAn/YbvGBhdNn6idmhgEikIPAjobi4JltdgUMHtsxTHHZEuJ7jWsllG19H/W/DzAXJFl9uYCRNU= X-Received: from pleg22.prod.google.com ([2002:a17:902:e396:b0:295:377d:bfc5]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:38c4:b0:297:df17:54cd with SMTP id d9443c01a7336-29b6becd454mr529105385ad.27.1764641016331; Mon, 01 Dec 2025 18:03:36 -0800 (PST) Reply-To: Sean Christopherson Date: Mon, 1 Dec 2025 18:03:32 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.52.0.107.ga0afd4fd5b-goog Message-ID: <20251202020334.1171351-1-seanjc@google.com> Subject: [PATCH 0/2] KVM: Fix a guest_memfd memslot UAF From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Potapenko , Sean Christopherson Content-Type: text/plain; charset="UTF-8" Fix a UAF due to leaving a dangling guest_memfd memslot binding by disallowing clearing KVM_MEM_GUEST_MEMFD on a memslot. The intent was that guest_memfd memslots would be immutable (could only be deleted), but somewhat ironically we missed the case where KVM_MEM_GUEST_MEMFD itself is the only flag that's toggled. This is an ABI change, but I can't imagine anyone was relying on disappearing a guest_memfd memslot. Patch 2 hardens against the UAF, and prepares for allowing FLAGS_ONLY changes on guest_memfd memslots. Sooner or later, we're going to allow dirty logging on guest_memfd, so I think it makes sense to guard against that so that whoever adds dirty logging support doesn't forget to unbind on a FLAGS_ONLY change. I'll respond with the syzkaller reproducer (it's comically simple). Sean Christopherson (2): KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot KVM: Harden and prepare for modifying existing guest_memfd memslots virt/kvm/kvm_main.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) base-commit: 115d5de2eef32ac5cd488404b44b38789362dbe6 -- 2.52.0.107.ga0afd4fd5b-goog