[PATCH 04/20] PCI/sysfs: Add CAP_SYS_ADMIN check to __resource_resize_store()

["Krzysztof Wilczyński" <kwilczynski@kernel.org>]

Currently, the __resource_resize_store() allows writing to the
resourceN_resize sysfs attribute to change a BAR's size without
checking for capabilities, currently relying only on the file
access check.

Resizing a BAR modifies PCI device configuration and can disrupt
active drivers.  After the upcoming conversion to static attributes,
it will also trigger resource file updates via sysfs_update_groups().

Thus, add a CAP_SYS_ADMIN check to prevent unprivileged users from
performing BAR resize operations.

Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
---
 drivers/pci/pci-sysfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index ac4e7c516e78..6b8c8e62f68a 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1619,6 +1619,9 @@ static ssize_t __resource_resize_store(struct device *dev, int n,
 	int ret;
 	u16 cmd;
 
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
 	if (kstrtoul(buf, 0, &size) < 0)
 		return -EINVAL;
 
-- 
2.53.0