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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e6ca4ef3esm6351460a91.1.2026.09.19.15.26.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 15:26:29 -0700 (PDT) From: Hui Peng To: bhelgaas@google.com, airlied@redhat.com Cc: linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH] PCI/VGA: fix inverted vga_tryget() return check and clear removed pci_dev Date: Sat, 19 Sep 2026 22:26:29 +0000 Message-ID: <20260919222629.3798073-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fix two issues in drivers/pci/vgaarb.c: 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);