From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B478AC982DE for ; Mon, 21 Sep 2026 10:40:04 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BFC7810E087; Mon, 21 Sep 2026 10:40:03 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="FZwH4CG1"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.4]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0895710E0D5 for ; Mon, 21 Sep 2026 10:40:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1789987202; x=1821523202; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=Ad6fpYFCwCgyEm0jJN8fMhX4f6iQUwkGcN+NiWPLSVk=; b=FZwH4CG1Hcg5uCLDjxDtv7t0/2HJUWmOQsqrTzTfBpV6MQQitUfccm/j bAub6R08JlAVRjd9O9WJTSyLQvW7llqJfIH9DToSn51IZGhqPecsShFlM Za0toVORGpUyHQ1cIjhzOGwH0tegRGdVuXYIMuLxe4oZe3RrCFC9ovZQN SIHVts5nBec/WgBQY4U8yeeoH6vzHDJFOEn4jvmKm+GchPgcLKk2qmCD/ fw2m0Ka0E+bnQK0Ce1MC3nNLiPNUtQNk1afrzG30fx3daKqYEOZ7frl0B mqZRoa1n4HUg1ylTuzrBMEtyw7/dKIqVQ00YswPLOZ3r74lwADKgNSIbS w==; X-CSE-ConnectionGUID: eP+FsLGDTROBMyPZnDkEAQ== X-CSE-MsgGUID: Q+oLdcEGQ7uLqKkjicXNiw== X-IronPort-AV: E=McAfee;i="6800,10657,11911"; a="995192" X-IronPort-AV: E=Sophos;i="6.27,114,1787036400"; d="scan'208";a="995192" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa114.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2026 03:40:02 -0700 X-CSE-ConnectionGUID: 8+XazXeCTmuTJA6Wr/tqcA== X-CSE-MsgGUID: mZc7qbq5SBS9jMbwFfsXTg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,114,1787036400"; d="scan'208";a="269116455" Received: from ettammin-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.244.180]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2026 03:40:00 -0700 From: Jani Nikula To: Hui Peng , bhelgaas@google.com, airlied@redhat.com Cc: linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI/VGA: fix inverted vga_tryget() return check and clear removed pci_dev In-Reply-To: <20260919222629.3798073-1-benquike@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: <20260919222629.3798073-1-benquike@gmail.com> Date: Mon, 21 Sep 2026 13:39:54 +0300 Message-ID: <21d4bbfe6facdf2f88b09b277bddfe0afff5e5a4@intel.com> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Sat, 19 Sep 2026, Hui Peng wrote: > Fix two issues in drivers/pci/vgaarb.c: One change per patch, please. > > 1. In vga_arb_device_init() / vga_arbiter_From_pci_dev(), vga_tryget() > returns 0 on success and a negative errno on failure, so checking if > (!vga_tryget(...)) is inverted and skips unlocking on success. > 2. In vga_arbiter_del_pci_device(), clear any open vga_arb_user_init > priv->target references pointing to the removed pci_dev so subsequent > writes or close() on /dev/vga_arbiter do not dereference a freed > pci_dev. > > Fixes: 1d38fe6ee6a8 ("PCI/VGA: Move vgaarb to drivers/pci") > Assisted-by: LLM > Signed-off-by: Hui Peng > --- > diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c > index 3de05aee7859..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; > } > @@ -1266,12 +1282,12 @@ 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; > } > > - if (vga_tryget(pdev, io_state)) { > + if (vga_tryget(pdev, io_state) == 0) { > /* Update the client's locks lists... */ > for (i = 0; i < MAX_USER_CARDS; i++) { > if (priv->cards[i].pdev == pdev) { > @@ -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); -- Jani Nikula, Intel