From 95e83e219d68956ba4fed9326683e4d2bd3e39a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= <kw@linux.com>
Date: Wed, 15 Sep 2021 23:01:25 +0000
Subject: [PATCH] PCI/sysfs: Check CAP_SYS_ADMIN before parsing user input
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Git-commit: 95e83e219d68956ba4fed9326683e4d2bd3e39a9
References: git-fixes
Patch-mainline: v5.16-rc1

Check if the "CAP_SYS_ADMIN" capability flag is set before parsing user
input as it makes more sense to first check whether the current user
actually has the right permissions before accepting any input from such
user.

This will also make order in which enable_store() and msi_bus_store()
perform the "CAP_SYS_ADMIN" capability check consistent with other
PCI-related sysfs objects that first verify whether user has this
capability set.

Link: https://lore.kernel.org/r/20210915230127.2495723-1-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/pci/pci-sysfs.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7fb5cd17cc98..6832e161be1c 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -273,15 +273,16 @@ static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 	unsigned long val;
-	ssize_t result = kstrtoul(buf, 0, &val);
-
-	if (result < 0)
-		return result;
+	ssize_t result;
 
 	/* this can crash the machine when done on the "wrong" device */
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	result = kstrtoul(buf, 0, &val);
+	if (result < 0)
+		return result;
+
 	device_lock(dev);
 	if (dev->driver)
 		result = -EBUSY;
@@ -378,12 +379,12 @@ static ssize_t msi_bus_store(struct device *dev, struct device_attribute *attr,
 	struct pci_bus *subordinate = pdev->subordinate;
 	unsigned long val;
 
-	if (kstrtoul(buf, 0, &val) < 0)
-		return -EINVAL;
-
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
 	/*
 	 * "no_msi" and "bus_flags" only affect what happens when a driver
 	 * requests MSI or MSI-X.  They don't affect any drivers that have
-- 
2.26.2