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 75936233722; Wed, 9 Sep 2026 14:19:52 +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=1788963593; cv=none; b=ngEwqVfqDFAdravsyWM+JQpciNimA9IOQ+ChbcZWWsjeH5SvnVX0L9wV0oBJ/+gDbm3gXw8meC38qmyqiqD1ZL0SLy6KYzXcgnlP167Jxz2a/p6mJluRmTr/vTHmBorpnpGEPYwznxaCw+ITDolBMvx4szJEBNGMI6Fq1jkkrRY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788963593; c=relaxed/simple; bh=M/xmyOD1GEk1HvpAIVzILBucqF8rEzFP/DgTTci688g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=YApSr1sKGUOxRh54kanlXEvWav4h3HoLS+iyENpEdKR5OsZh+09AtdqG91jWAnI2276TcCADdSibP/Aczd9dpeEGiB2hzFcQ2zApuQWtJ9raasbQc3mfKgZxCoWGsHHMixQB4uxt4B92aN1mCc1jmw15TkPusIt0MYUjORdmPjQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=q4WyC/q3; 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="q4WyC/q3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEAB91F00A3A; Wed, 9 Sep 2026 14:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788963592; bh=QPKN7QKJtqlH98bG1oTGTxQjji5NiScdP8uARJRxTCo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=q4WyC/q3K/0/cgjJcSgeSiG+wSRf3p1IlRzTY7SgpNnTVv8OJmAVKG/edHKJjfdRK qF+k29GArM9OsJ6uE5INCXRq7UkxWHpd8cOqEYvJYn1CwoJD92Udh1dqNWxpj8O2hx SgrErqKj+/0cPM3HV2Faxe+1KjnzsVBuelSgeQs8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Anthony Krowiak , Matthew Rosato , Christian Borntraeger Subject: [PATCH 6.18 133/583] s390/vfio-ap: Fix NULL deref in status_show() during queue probe Date: Wed, 9 Sep 2026 15:36:58 +0200 Message-ID: <20260909134242.748911957@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134237.773280130@linuxfoundation.org> References: <20260909134237.773280130@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Anthony Krowiak commit dd6f4ef6f8a37412909ad787c837332fb070159c upstream. When vfio_ap_mdev_probe_queue() creates the sysfs attribute group, the queue's driver data has not yet been set. A concurrent read of the 'status' attribute can therefore call dev_get_drvdata() and get NULL, which is then passed directly to vfio_ap_mdev_for_queue() where q->apqn is unconditionally dereferenced, causing a NULL pointer dereference. Fix this by acquiring the update locks before calling sysfs_create_group(). The status_show() function acquires guests_lock before reading the driver data, so any concurrent read will block until after dev_set_drvdata() has been called and the update locks are released. As a bonus, the APQN no longer needs to be read from the queue struct after allocation — it can be read directly from apdev before allocation and stored in a local variable, which is then assigned to q->apqn once the allocation succeeds. Fixes: 260f3ea141382 ("s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c") Cc: stable@vger.kernel.org Signed-off-by: Anthony Krowiak Reviewed-by: Matthew Rosato Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman --- drivers/s390/crypto/vfio_ap_ops.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) --- a/drivers/s390/crypto/vfio_ap_ops.c +++ b/drivers/s390/crypto/vfio_ap_ops.c @@ -2321,6 +2321,23 @@ static ssize_t status_show(struct device mutex_lock(&matrix_dev->guests_lock); mutex_lock(&matrix_dev->mdevs_lock); q = dev_get_drvdata(&apdev->device); + + /* + * Make sure the drvdata has been set before proceeding. There is a + * possibility that the drvdata was not set if the vfio_ap_queue object + * could not be allocated when the queue device was probed. In that case, + * the locks used in vfio_ap_mdev_probe_queue() are released prior to + * removing the sysfs status attribute to avoid a lockdep + * splat. That opens a very small window where the status attribute is + * still available without the vfio_ap_queue object having been + * stored in the device drvdata. In that case, indicate the queue is not + * assigned. + */ + if (!q) { + nchars = sysfs_emit(buf, "%s\n", AP_QUEUE_UNASSIGNED); + goto done; + } + matrix_mdev = vfio_ap_mdev_for_queue(q); /* If the queue is assigned to the matrix mediated device, then @@ -2345,6 +2362,7 @@ static ssize_t status_show(struct device nchars = sysfs_emit(buf, "%s\n", AP_QUEUE_UNASSIGNED); } +done: mutex_unlock(&matrix_dev->mdevs_lock); mutex_unlock(&matrix_dev->guests_lock); @@ -2419,14 +2437,17 @@ void vfio_ap_mdev_unregister(void) int vfio_ap_mdev_probe_queue(struct ap_device *apdev) { - int ret; + int ret, apqn; struct vfio_ap_queue *q; DECLARE_BITMAP(apm_filtered, AP_DEVICES); struct ap_matrix_mdev *matrix_mdev; + apqn = to_ap_queue(&apdev->device)->qid; + matrix_mdev = get_update_locks_by_apqn(apqn); + ret = sysfs_create_group(&apdev->device.kobj, &vfio_queue_attr_group); if (ret) - return ret; + goto err_release_locks; q = kzalloc(sizeof(*q), GFP_KERNEL); if (!q) { @@ -2434,11 +2455,10 @@ int vfio_ap_mdev_probe_queue(struct ap_d goto err_remove_group; } - q->apqn = to_ap_queue(&apdev->device)->qid; + q->apqn = apqn; q->saved_isc = VFIO_AP_ISC_INVALID; memset(&q->reset_status, 0, sizeof(q->reset_status)); INIT_WORK(&q->reset_work, apq_reset_check); - matrix_mdev = get_update_locks_by_apqn(q->apqn); if (matrix_mdev) { vfio_ap_mdev_link_queue(matrix_mdev, q); @@ -2467,8 +2487,13 @@ done: return ret; err_remove_group: + release_update_locks_for_mdev(matrix_mdev); sysfs_remove_group(&apdev->device.kobj, &vfio_queue_attr_group); return ret; + +err_release_locks: + release_update_locks_for_mdev(matrix_mdev); + return ret; } void vfio_ap_mdev_remove_queue(struct ap_device *apdev)