PCI: Fix reset_method_store() memory leak

In reset_method_store(), a string is allocated via kstrndup() and assigned
to the local "options". options is then used in with strsep() to find
spaces:

  while ((name = strsep(&options, " ")) != NULL) {

If there are no remaining spaces, then options is set to NULL by strsep(),
so the subsequent kfree(options) doesn't free the memory allocated via
kstrndup().

Fix by using a separate tmp_options to iterate with strsep() so options is
preserved.

Link: https://lore.kernel.org/r/20241001231147.3583649-1-tkjos@google.com
Fixes: d88f521 ("PCI: Allow userspace to query and set device reset mechanism")
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: toddkjos

drivers/pci/pci.c

@@ -5244,7 +5244,7 @@ static ssize_t reset_method_store(struct device *dev,
 				  const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	char *options, *name;
+	char *options, *tmp_options, *name;
 	int m, n;
 	u8 reset_methods[PCI_NUM_RESET_METHODS] = { 0 };
 
@@ -5264,7 +5264,8 @@ static ssize_t reset_method_store(struct device *dev,
 		return -ENOMEM;
 
 	n = 0;
-	while ((name = strsep(&options, " ")) != NULL) {
+	tmp_options = options;
+	while ((name = strsep(&tmp_options, " ")) != NULL) {
 		if (sysfs_streq(name, ""))
 			continue;