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 CB97D175A88; Sat, 8 Aug 2026 17:49:55 +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=1786211397; cv=none; b=NfOcaMxc0itsszqCJSAEv6GA2YCPPF24BErdw9z2i2XHPcwZRV/3DLuspbv1LawxCVZz5DlCVd1Hu6TKJos1Mt15dlZiFg3UvkVdqa3kmcSniInkG37nhgy1uaK2wggpphRxABQWxGECURbdMAyS90kzhGGlrFBWGsQZTEXKZUk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786211397; c=relaxed/simple; bh=ALztxF0QNUBml+fzzpI3VPI9kkn/PSmNBg9uapRCTc4=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=Zs63K1GmtSZtdaZt2NzvfeIVNfNUBHLQiJ/RWOyLUshcMPKnmKZ1sM7j9JiKT7TVYX/qOM7mMEtSCbbpG55xq7ELvLBoDso80cTQMLQJsj1Mt8cJ0LLTfDLOS4Lecv0hiAgKxHZSA6kk3SAoNf/McvfH1TPOsnr15fJF9tssNO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DgUdqFiy; 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="DgUdqFiy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 163381F000E9; Sat, 8 Aug 2026 17:49:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786211395; bh=GuhKGEFznq7tiATRMV7BqJZ4iU00My3cOQnh6yhcSoQ=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=DgUdqFiyNiy93Oeyf0RTRidDHDsY1DBlJkKskxFfdOjGNrsWbUlE6pGoNYrp78Lf3 RmOdXZcRCEDDgVVCmTnQk1ZKIevw456OOY2qD5mrnKVkEjl7dHrOwtrtBGD3J9wQJe ff4Onn/2O8mzWNQarm1LUPWlAwquSm8+k9M52EPbrzMeoBzcxMJv6klNIGsareUdEZ dNbHOT71h2ZtmUjehVxPHj4Du6hsmRs7UOc+W/VgTK3/zb9fGNilKUocIjO+U1EjWC EcgI9a5QqTNO5MRztkh7YwhHuYgSQ4vyPs3/ktuTbYtu+638fTBijdb8v0byX88R8W bFMMBsgqxdaFQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH 1/5] s390/vfio-ap: Fix stale do_remove flag across iterations in vfio_ap_mdev_cfg_remove Reply-To: sashiko-reviews@lists.linux.dev To: "Anthony Krowiak" Cc: "Alexander Gordeev" , kvm@vger.kernel.org, linux-s390@vger.kernel.org, "Heiko Carstens" , "Vasily Gorbik" In-Reply-To: <20260808170712.839066-2-akrowiak@linux.ibm.com> References: <20260808170712.839066-1-akrowiak@linux.ibm.com> <20260808170712.839066-2-akrowiak@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sat, 08 Aug 2026 17:49:54 +0000 Message-Id: <20260808174955.163381F000E9@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 4 potential issue(= s) to consider: Pre-existing issues: - [Critical] Unconditional dereference of `matrix_mdev->kvm` pointer leadin= g to host kernel panic. - [High] Concurrent modification and traversal of `matrix_dev->mdev_list` w= ithout consistent locking. - [High] Assigned control domains removed from the host are not unplugged f= rom the KVM guest due to incorrect bitmap calculation. - [High] Unplugging the last assigned AP resource from an mdev fails to upd= ate the KVM guest configuration. -- --- Patch [1]: [PATCH 1/5] s390/vfio-ap: Fix stale do_remove flag across it= erations in vfio_ap_mdev_cfg_remove --- commit bb84df1768da7fbde04fb6494c22c41ed756bd46 Author: Anthony Krowiak s390/vfio-ap: Fix stale do_remove flag across iterations in vfio_ap_mdev_cf= g_remove This commit fixes an issue in vfio_ap_mdev_cfg_remove() where the do_remove flag is incorrectly accumulated across iterations. It ensures the flag is properly assigned on the first bitmap operation for each mdev. > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio= _ap_ops.c > index 44b3a1dcc1b36..845c86ba8bc30 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -2603,15 +2603,15 @@ static void vfio_ap_mdev_cfg_remove(unsigned long= *ap_remove, > DECLARE_BITMAP(aprem, AP_DEVICES); > DECLARE_BITMAP(aqrem, AP_DOMAINS); > DECLARE_BITMAP(cdrem, AP_DOMAINS); > - int do_remove =3D 0; > + int do_remove; > =20 > list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) { [Severity: High] This isn't a bug introduced by this patch, but does this code risk list corruption or following invalid pointers? The list is being iterated without holding mdevs_lock across the entire loop (the lock is acquired and released inside the loop). Concurrently, vfio_ap_mdev_probe() adds new mdevs to the list while holding only mdevs_lo= ck: drivers/s390/crypto/vfio_ap_ops.c:vfio_ap_mdev_probe() { ... list_add(&matrix_mdev->node, &matrix_dev->mdev_list); ... } Could this concurrent modification and traversal crash the host kernel? > mutex_lock(&matrix_mdev->kvm->lock); [Severity: Critical] This is a pre-existing issue, but can this unconditionally dereference a nu= ll pointer? When an mdev is created, its kvm pointer is null until it is attached to a guest. If a host AP configuration change occurs while an unattached mdev exists, this unconditionally executes mutex_lock(&matrix_mdev->kvm->lock), which dereferences the null kvm pointer. Could this lead to a host kernel panic? > mutex_lock(&matrix_dev->mdevs_lock); > =20 > - do_remove |=3D bitmap_and(aprem, ap_remove, > - matrix_mdev->matrix.apm, > - AP_DEVICES); > + do_remove =3D bitmap_and(aprem, ap_remove, > + matrix_mdev->matrix.apm, > + AP_DEVICES); > do_remove |=3D bitmap_and(aqrem, aq_remove, > matrix_mdev->matrix.aqm, > AP_DOMAINS); [Severity: High] This is a pre-existing issue in vfio_ap_mdev_cfg_remove(), but is this bitm= ap calculation correct? Right below the quoted code, cdrem is calculated: drivers/s390/crypto/vfio_ap_ops.c:vfio_ap_mdev_cfg_remove() { ... do_remove |=3D bitmap_andnot(cdrem, cd_remove, matrix_mdev->matrix.adm, AP_DOMAINS); ... } This evaluates to cd_remove & ~(matrix.adm), which yields domains removed f= rom the host that are explicitly not assigned to the mdev. Assigned domains that are removed from the host are omitted and therefore not hot-unplugged. Could this allow a control domain removed from the host AP configuration to remain improperly assigned and accessible to the KVM guest? [Severity: High] This is another pre-existing issue, but does unplugging the last assigned AP resource from an mdev fail to update the KVM guest configuration? In vfio_ap_mdev_hot_unplug_cfg(), do_hotplug is determined using bitmap_and= not: drivers/s390/crypto/vfio_ap_ops.c:vfio_ap_mdev_hot_unplug_cfg() { ... if (!bitmap_empty(aprem, AP_DEVICES)) { do_hotplug |=3D bitmap_andnot(matrix_mdev->shadow_apcb.apm, matrix_mdev->shadow_apcb.apm, aprem, AP_DEVICES); } ... } bitmap_andnot returns true only if the resulting destination bitmap is non-empty. If the last adapter or domain is removed, the resulting mask is empty, bitmap_andnot returns false, and do_hotplug remains false. Would this skip the APCB update, leaving the KVM guest with its old KVM CRY= CBD configuration and retaining access to an AP resource that was successfully removed from the host? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260808170712.8390= 66-1-akrowiak@linux.ibm.com?part=3D1