Commit 9fb0eed0 authored Oct 20, 2023 by Armin Wolf Committed by Greg Kroah-Hartman Nov 20, 2023

platform/x86: wmi: Fix opening of char device



[ Upstream commit eba9ac7abab91c8f6d351460239108bef5e7a0b6 ]

Since commit fa1f68db ("drivers: misc: pass miscdevice pointer via
file private data"), the miscdevice stores a pointer to itself inside
filp->private_data, which means that private_data will not be NULL when
wmi_char_open() is called. This might cause memory corruption should
wmi_char_open() be unable to find its driver, something which can
happen when the associated WMI device is deleted in wmi_free_devices().

Fix the problem by using the miscdevice pointer to retrieve the WMI
device data associated with a char device using container_of(). This
also avoids wmi_char_open() picking a wrong WMI device bound to a
driver with the same name as the original driver.

Fixes: 44b6b766 ("platform/x86: wmi: create userspace interface for drivers")
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20231020211005.38216-5-W_Armin@gmx.de


Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 22117b77

drivers/platform/x86/wmi.c

+6 −14

Original line number	Diff line number	Diff line
		@@ -817,21 +817,13 @@ static int wmi_dev_match(struct device dev, struct device_driver driver)
		}
		static int wmi_char_open(struct inode inode, struct file filp)
		{
		const char *driver_name = filp->f_path.dentry->d_iname;
		struct wmi_block *wblock;
		struct wmi_block *next;
		/*
		* The miscdevice already stores a pointer to itself
		* inside filp->private_data
		*/
		struct wmi_block *wblock = container_of(filp->private_data, struct wmi_block, char_dev);

		list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
		if (!wblock->dev.dev.driver)
		continue;
		if (strcmp(driver_name, wblock->dev.dev.driver->name) == 0) {
		filp->private_data = wblock;
		break;
		}
		}

		if (!filp->private_data)
		return -ENODEV;

		return nonseekable_open(inode, filp);
		}