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 53E623A75B6; Tue, 28 Jul 2026 17:25:38 +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=1785259539; cv=none; b=cKIcD1dEzN1W+P2QtuRpnhVwXoAnLiXiWhFw9+GVjjTVxnMnOFsV0kOzPWRQK0JaX4eFW/cYovUdQczwIoLg6jaBxnwbXwHI3r0P7T8ZYKFCHAwlnQk/bHQo+KZeiKB0r5cbufY2iwzAQSuEsaDZ34nhNnuWyGwWvBvcbNKA52w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785259539; c=relaxed/simple; bh=J+fe8oMvpNufqTFyZibH3lMwf2OYmKxp+mHNHujU1vo=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=HGwyIas0+sFIqT997xcy23yzt/6F4FNXRXELmYSgx4IV+UqBxkX6UVjbObnfoAARpVhRu1SgIV/7kZW/MYdUz6kTCJXFOLS4YHJd+42dCo4qMS6ojzqY8l0oR9g91TPY7Co4WtSmILNIU89dvlAGsjLKvFj2TV0knnSxHT7QUFw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m/uydPeY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m/uydPeY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9832C1F000E9; Tue, 28 Jul 2026 17:25:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785259537; bh=GVF+6/FpMmNQOLETJYYbnRoOe+zrVwOpiDKNL8+ixNQ=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=m/uydPeYAXd4lJ7893jP7LH2kE9oYhn8kWAJuAY8SLMKyn5bRMoE3iSTc90UFlT69 1V8RITTaHbi5jSnx7d80NyrPf2jSXOs8v0nyyCK0yr6BjtztzD3R0N79kB0FLuWzmE ubKIiNm22e8BlMh9S3vQbl2XvDzMG0JpGqLV5KRiY563jYXm6vRQpvEmIDZ2xk0JQO QTP+JVAxSiVQjUFTHsywRuVg+RjYyXnGGQSXybOw8gwkd+LFOytBmnbdnSsFD2i40l VlEVbZj73vnsitZGHxP8cX4DIlOa48eIp+KRpHaw1gUw3e9wwEAurIxQUluAbdHdPZ DofORP3AHE2OQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 11/13] KVM: s390: Fix kvm_arch_commit_memory_region() when low on memory Reply-To: sashiko-reviews@lists.linux.dev To: "Claudio Imbrenda" Cc: "Heiko Carstens" , "Vasily Gorbik" , linux-s390@vger.kernel.org, "Alexander Gordeev" , kvm@vger.kernel.org In-Reply-To: <20260728170708.294400-12-imbrenda@linux.ibm.com> References: <20260728170708.294400-1-imbrenda@linux.ibm.com> <20260728170708.294400-12-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 28 Jul 2026 17:25:37 +0000 Message-Id: <20260728172537.9832C1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] User-triggerable KVM_BUG_ON (WARN_ON_ONCE) on memcg OOM. -- --- Patch [11]: [PATCH v4 11/13] KVM: s390: Fix kvm_arch_commit_memory_regi= on() when low on memory --- commit 9bd2f3fe880640681d24faea9af3bd26f006d538 Author: Claudio Imbrenda KVM: s390: Fix kvm_arch_commit_memory_region() when low on memory =20 When low on memory, kvm_arch_commit_memory_region() attempts to refill the MMU cache and retry. If the refill fails, it kills the VM using KVM_BUG_ON. > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c [ ... ] > @@ -5850,11 +5848,17 @@ void kvm_arch_commit_memory_region(struct kvm *kv= m, > case KVM_MR_FLAGS_ONLY: > break; > default: > + rc =3D 0; > WARN(1, "Unknown KVM MR CHANGE: %d\n", change); > } > } > + if (rc =3D=3D -ENOMEM) { > + rc =3D kvm_s390_mmu_cache_topup(mc); > + if (!rc) > + goto retry; > + } > out: > - if (rc) > + if (KVM_BUG_ON(rc, kvm)) [Severity: High] Could this KVM_BUG_ON() be triggered by a host-userspace process facing memory pressure? If an unprivileged userspace process creates a VM within a restricted memory cgroup (memcg), and then calls KVM_SET_USER_MEMORY_REGION to modify a memslot, kvm_s390_mmu_cache_topup() could return -ENOMEM due to the memcg limit. Since KVM_BUG_ON expands to WARN_ON_ONCE, wouldn't this allow a malicious guest or unprivileged host process to cause a host-side denial of service if panic_on_warn is enabled? > pr_warn("failed to commit memory region\n"); > return; > } --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260728170708.2944= 00-1-imbrenda@linux.ibm.com?part=3D11