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 5F39C3242BA for ; Fri, 11 Sep 2026 01:13:21 +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=1789089205; cv=none; b=YsEG0tonLFvztzvDUuTdQBUOGA5O6PgF3TGXWK4j7uE2SqLpIQwHn43UUCc+nkwE+zgYEYPqnW9ySPwaIic39hbd2MyvuXkMsg2Sb1mDMDvfVOutZc8SmLuHnSg4SIqy2MBMt5K+y9I8ofgsIYf/f+FTq8BBhlESlF1rFer8DsQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789089205; c=relaxed/simple; bh=W4iKbohOFMKndN9gJhR7aTQUCH8WPX0lQdyWqZHDwws=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WONxgTFzIbvZIt/bux98fsB3t3hbi/qPKgiE7lrhvs+YVMsWVvmvQRn9dK1QIK72N2rQqq+YMA3c5xWJkfuclyVMPznAwmSwYt/0cbNBjL6d5GbYnKjfGCdt62ioadV6OakSpKlJSEV4ASKIrTxtZIvpDIZkaiRL4AE7s9f/pXA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SM/infUh; 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="SM/infUh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B39CD1F0089D; Fri, 11 Sep 2026 01:13:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789089200; bh=VisMz8FHKRP5dTAvhsQ6+tBmaH3QNzCDw9l/qFZ+HvQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SM/infUhS3s3+Kj4V7T3HyFtXdo85iqsws39KsCJ1LiSgJusiI8IVracPOXx6tHpr /AlzKBQ6G+apvYXfNUKhlrkRtP4z5AJ23Ez0qJRraWw/MWL1Xhe1VweAdcxd6uu2q2 T78Z2VYeHzfP6ePAwueoPKzGrpLxBt2gZwFPHfW5brW28yHfPX3VcihkI2Rspke0cU i2R0J4OYf0SZqrfWCG7qwr3Na19+YuMkhTePNzc1NVin6anqim0mtiav5IAf5GgheS E91vElx15ohHpaHnk1K/Dw3+5/0mFXS0h6qnSo7UwlxsRo4ma+po3snEfEh+dD45Q2 CccoB7wsyd2PQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Anthony Krowiak , Matthew Rosato , Christian Borntraeger , Sasha Levin Subject: [PATCH 6.1.y] s390/vfio-ap: Fix NULL deref in status_show() during queue probe Date: Thu, 10 Sep 2026 21:13:17 -0400 Message-ID: <20260911011317.4035178-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090930-overcrowd-probiotic-71cb@gregkh> References: <2026090930-overcrowd-probiotic-71cb@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Anthony Krowiak [ Upstream commit dd6f4ef6f8a37412909ad787c837332fb070159c ] 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 [ Adjusted queue-initialization context because Linux 6.1 lacks the newer reset fields. ] Signed-off-by: Sasha Levin --- drivers/s390/crypto/vfio_ap_ops.c | 33 +++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c index 11fe917fbd9d4..3eb6cd604bed6 100644 --- a/drivers/s390/crypto/vfio_ap_ops.c +++ b/drivers/s390/crypto/vfio_ap_ops.c @@ -1768,6 +1768,23 @@ static ssize_t status_show(struct device *dev, 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 @@ -1795,6 +1812,7 @@ static ssize_t status_show(struct device *dev, AP_QUEUE_UNASSIGNED); } +done: mutex_unlock(&matrix_dev->mdevs_lock); return nchars; @@ -1864,13 +1882,16 @@ 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; 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) { @@ -1878,9 +1899,8 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev) goto err_remove_group; } - q->apqn = to_ap_queue(&apdev->device)->qid; + q->apqn = apqn; q->saved_isc = VFIO_AP_ISC_INVALID; - matrix_mdev = get_update_locks_by_apqn(q->apqn); if (matrix_mdev) { vfio_ap_mdev_link_queue(matrix_mdev, q); @@ -1907,8 +1927,13 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev) return 0; 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) -- 2.53.0