From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f13.google.com (mail-pj2-f13.google.com [74.125.227.141]) (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 169ED78F3A for ; Mon, 21 Sep 2026 05:27:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.141 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789968433; cv=none; b=VDFql3jmShDn7+l4AzYR9KX2K/Y87HPMtjmx1xz50s3OJFuGAWttxbkLe/+UiKtqYpr0B8TuHTHYvpWtpyIslBZK1Z0ZQtEHyuyUe9Ocw6tKNJy4NbbMynhpCIrJAFmxCb7v+U4JJnbcZbt6z7nrnP5W4oRbTQAXJXWYvkbNN5I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789968433; c=relaxed/simple; bh=EWu1pLVFRSaebwmi7fm/KMUICrHPC3ue7UZVQJg/fhY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ipwG7XT6Gx0InRC3WoSMA/0wWeKA/7ifb9FoqcnDgybmVpcIE77dOo7bJYz7kupGFKCDKVAvv92uSAmad0dFH8vR3IdqCqIoEc8XvLyaq8KH1S1ttUlfBPLrkJHCzm/YvLb9lQuVlvzmovguBUb4ZKxe2PpQXkgOQ9VD0fQkqxE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jLlmAY8t; arc=none smtp.client-ip=74.125.227.141 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jLlmAY8t" Received: by mail-pj2-f13.google.com with SMTP id 98e67ed59e1d1-396ccb1a98dso1940723a91.0 for ; Sun, 20 Sep 2026 22:27:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789968425; x=1790573225; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=Xz7oDjDIsYHvot04hwnpj8aBarD/yeH6H4D2rmaqZdc=; b=jLlmAY8toK3ay6YjxLCbenY4BHriYZL65+6EmqZQPoycLR0fNt9F5euKFcsfs5zKjl DEnpk4BpFQu7GCyRbLfRitlWQqwBl7dhptmF5YSsxIarnEucAg6eBL8ADanIfqC/S6+W 66bj+oI+Ve9VCHx3q6TJGGPxloRvdziynTNv7OquM3iXaK3aVaGf/WuvC2obSgCTRDfB Y8yYK/4EqvwtpFBDIqC+1Fmq2xnDCtih0QjVtXldfpAGZOjYP/qwpUufoR7qR1MW4Qvb KZgKzfezrgsNwTkeCyAL5/Lw07oHVPV0Cz0Is5t74cVG/o3j8iQfgW86XOfzfF4gdnLw RiyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789968425; x=1790573225; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=Xz7oDjDIsYHvot04hwnpj8aBarD/yeH6H4D2rmaqZdc=; b=LhdDq/uyefYRyzMU9AZ8m2ActtzgBYiIJRalaxLoMb4lrtWkhNHjGIra++OL7swGCw cnv/SiarRpjKjoDok3nH30nj0NtB0H+Xes9sflnohd9O5GZfESx2dnyE/r5ZOpanz5Bj k2IjQrr5tP8uxU9L9hrTdAePn2lDNthTs0Vr9+/k/jNTWg8PQN4Bvfl/PJYaOV/5tP7X 0REX4pPQZ3qy1TUrAVCb18nF+2CqBOaUnKJUc19z41zXfii+vAY+enmVRJ+nU4bn2KZP wrOHEmsxpiYfRiJdAnTxP+qqEWF4fbCtarxJloVX3LLWJ1igdByNdy54mGe57F1aom5b kdEA== X-Forwarded-Encrypted: i=1; AKwUvBzzc5zHQv6Lfufb0ajBwAg9SoYiYWzaGDjaIorQt+ZufSr/gopNUP28RxAes/GuLaHXhS9BEgLtkmI=@vger.kernel.org X-Gm-Message-State: AFuF++mnO36/tA0am6H79f1Lg/whEwMbCoVMdi7cR6Cg6hCV2FnuBayG HxwgiD72Wo2hbh6u6QbWoRKjOkcvFhfChlDxSVOXyC3Dj0lGWtP5NPqp X-Gm-Gg: AYBFou1l1GnPPjh3Zf1nzEG4Z51OqoV0GWIbry35dWDBOhGzrBAFpRgUicbynos8SzA kWXNl+ZPNZwbG+3/zZoQ1ayMb5lhxsFoiHEV1m9H38qS2o54gU1vtNJzpV18T6kDFPy8s9/Ol6v cXfe41dk83LsYoGU6JzjSJTSz25bp0yvW9Tecv5ADrLdizcuE254fmLtFcMxhbyq4PQ/QyCJCpJ SOBCoOCIQRGZp7OgPE+0PLwz+f+HjcMhND4UdBTzhNWxqD00fEHt2Xk8DZV5VSM9Li5xW5hc41Q wHDsbQLwcrXTIAJwJmndnRdjaX4w1TvSKQF7UzkqgBbkTP0bmEFBNTY2kc/xjgGYfpNEMMFsPHS AH4SuPWxBxi4E64CmJjXd2wkCH1AU9qFyy3Vre3HuPh+A0hkf11stJbBo0kBms9MZGHUpufP16b C8BCbhcCcZAR0mNeyaWacQJ0wLEF2JXeed0kJehWkvZmSiubXMZN7kdXM/vVjVgQEUcl50Xuvig 2sFmZkmgpK0+aoXvSKHd4F1ObjWdDZcslhwtt3IN+hESt6zpyx+Om+vOvGiAAYyzygpBlJNg/Lg ueDi/YlySQ== X-Received: by 2002:a17:90b:554b:b0:39e:6c6a:6574 with SMTP id 98e67ed59e1d1-39e6c6a6819mr9043191a91.55.1789968425257; Sun, 20 Sep 2026 22:27:05 -0700 (PDT) Received: from phui-2.c.googlers.com.com (67.51.127.34.bc.googleusercontent.com. [34.127.51.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e554e5529sm6677054a91.4.2026.09.20.22.27.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Sep 2026 22:27:04 -0700 (PDT) From: Hui Peng To: bhelgaas@google.com, airlied@redhat.com Cc: benh@kernel.crashing.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, benquike@gmail.com Subject: [PATCH v2 2/2] PCI/VGA: invalidate open user references in vga_arbiter_del_pci_device() Date: Mon, 21 Sep 2026 05:27:02 +0000 Message-ID: <20260921052702.1725696-2-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog In-Reply-To: <20260921052702.1725696-1-benquike@gmail.com> References: <20260919222629.3798073-1-benquike@gmail.com> <20260921052702.1725696-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a PCI VGA device is removed while /dev/vga_arbiter is open, vga_arbiter_del_pci_device() removes and frees the vgadev entry, but any open struct vga_arb_private on vga_user_list retains dangling pointers to the removed pdev in priv->target and priv->cards[i].pdev. Subsequent writes to /dev/vga_arbiter or closing the file descriptor in vga_arb_release() dereference the removed pdev. Mark matching priv->target and priv->cards[i].pdev entries as PCI_INVALID_CARD under vga_user_lock in vga_arbiter_del_pci_device(), and treat PCI_INVALID_CARD like NULL in vga_arb_write() and vga_arb_release(). Tested in QEMU against Linux 7.3.0-rc3 by opening /dev/vga_arbiter, selecting PCI:0000:00:02.0, hot-removing the PCI VGA device via /sys/bus/pci/devices/0000:00:02.0/remove, and writing "unlock io+mem". On the unfixed kernel, priv->target retains a dangling pointer to the removed pci_dev so write("unlock io+mem") proceeds past the NULL check and returns -EINVAL (-22); with this patch applied, priv->target is set to PCI_INVALID_CARD on removal and write("unlock io+mem") immediately returns -ENODEV (-19). Fixes: deb2d2ecd43d ("PCI/GPU: implement VGA arbitration on Linux") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v2: - Split out from the vga_tryget() return check fix into patch 2/2. - Update Fixes: tag from the file-move commit 1d38fe6ee6a8 to deb2d2ecd43d ("PCI/GPU: implement VGA arbitration on Linux"). drivers/pci/vgaarb.c | 71 +++++++++++++++++++++++++++----------------- 1 file changed, 44 insertions(+), 27 deletions(-) diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c index 350ab9624eb9..4f13e542505a 100644 --- a/drivers/pci/vgaarb.c +++ b/drivers/pci/vgaarb.c @@ -818,11 +818,33 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev) return false; } +#define MAX_USER_CARDS CONFIG_VGA_ARB_MAX_GPUS +#define PCI_INVALID_CARD ((struct pci_dev *)-1UL) + +/* Each user has an array of these, tracking which cards have locks */ +struct vga_arb_user_card { + struct pci_dev *pdev; + unsigned int mem_cnt; + unsigned int io_cnt; +}; + +struct vga_arb_private { + struct list_head list; + struct pci_dev *target; + struct vga_arb_user_card cards[MAX_USER_CARDS]; + spinlock_t lock; +}; + +static LIST_HEAD(vga_user_list); +static DEFINE_SPINLOCK(vga_user_lock); + static bool vga_arbiter_del_pci_device(struct pci_dev *pdev) { struct vga_device *vgadev; + struct vga_arb_private *priv; unsigned long flags; bool ret = true; + int i; spin_lock_irqsave(&vga_lock, flags); vgadev = vgadev_find(pdev); @@ -845,6 +867,21 @@ static bool vga_arbiter_del_pci_device(struct pci_dev *pdev) wake_up_all(&vga_wait_queue); bail: spin_unlock_irqrestore(&vga_lock, flags); + if (ret) { + spin_lock_irqsave(&vga_user_lock, flags); + list_for_each_entry(priv, &vga_user_list, list) { + if (priv->target == pdev) + priv->target = PCI_INVALID_CARD; + for (i = 0; i < MAX_USER_CARDS; i++) { + if (priv->cards[i].pdev == pdev) { + priv->cards[i].pdev = PCI_INVALID_CARD; + priv->cards[i].io_cnt = 0; + priv->cards[i].mem_cnt = 0; + } + } + } + spin_unlock_irqrestore(&vga_user_lock, flags); + } kfree(vgadev); return ret; } @@ -1025,27 +1062,6 @@ EXPORT_SYMBOL(vga_client_register); * the arbiter. */ -#define MAX_USER_CARDS CONFIG_VGA_ARB_MAX_GPUS -#define PCI_INVALID_CARD ((struct pci_dev *)-1UL) - -/* Each user has an array of these, tracking which cards have locks */ -struct vga_arb_user_card { - struct pci_dev *pdev; - unsigned int mem_cnt; - unsigned int io_cnt; -}; - -struct vga_arb_private { - struct list_head list; - struct pci_dev *target; - struct vga_arb_user_card cards[MAX_USER_CARDS]; - spinlock_t lock; -}; - -static LIST_HEAD(vga_user_list); -static DEFINE_SPINLOCK(vga_user_lock); - - /* * Take a string in the format: "PCI:domain:bus:dev.fn" and return the * respective values. If the string is not in this format, return 0. @@ -1168,7 +1184,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf, } pdev = priv->target; - if (priv->target == NULL) { + if (priv->target == NULL || priv->target == PCI_INVALID_CARD) { ret_val = -ENODEV; goto done; } @@ -1215,7 +1231,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf, } pdev = priv->target; - if (priv->target == NULL) { + if (priv->target == NULL || priv->target == PCI_INVALID_CARD) { ret_val = -ENODEV; goto done; } @@ -1266,7 +1282,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf, */ pdev = priv->target; - if (priv->target == NULL) { + if (priv->target == NULL || priv->target == PCI_INVALID_CARD) { ret_val = -ENODEV; goto done; } @@ -1335,7 +1351,8 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf, for (i = 0; i < MAX_USER_CARDS; i++) { if (priv->cards[i].pdev == pdev) break; - if (priv->cards[i].pdev == NULL) { + if (priv->cards[i].pdev == NULL || + priv->cards[i].pdev == PCI_INVALID_CARD) { priv->cards[i].pdev = pdev; priv->cards[i].io_cnt = 0; priv->cards[i].mem_cnt = 0; @@ -1366,7 +1383,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf, goto done; } pdev = priv->target; - if (priv->target == NULL) { + if (priv->target == NULL || priv->target == PCI_INVALID_CARD) { ret_val = -ENODEV; goto done; } @@ -1429,7 +1446,7 @@ static int vga_arb_release(struct inode *inode, struct file *file) list_del(&priv->list); for (i = 0; i < MAX_USER_CARDS; i++) { uc = &priv->cards[i]; - if (uc->pdev == NULL) + if (uc->pdev == NULL || uc->pdev == PCI_INVALID_CARD) continue; vgaarb_dbg(&uc->pdev->dev, "uc->io_cnt == %d, uc->mem_cnt == %d\n", uc->io_cnt, uc->mem_cnt); -- 2.49.0