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platform/x86: wmi: Fix opening of char device

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[ Upstream commit eba9ac7aba ]

Since commit fa1f68db6c ("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: 44b6b76611 ("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>
This commit is contained in:
Armin Wolf 2023-10-20 23:10:04 +02:00 committed by Greg Kroah-Hartman
parent c57e81d5e5
commit e0bf076b73
1 changed files with 6 additions and 14 deletions
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20
drivers/platform/x86/wmi.c
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@ -827,21 +827,13 @@ 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;
filp->private_data = wblock;
return nonseekable_open(inode, filp);
}