4.19-stable review patch. If anyone has any objections, please let me know.
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From: Armin Wolf W_Armin@gmx.de
[ Upstream commit eba9ac7abab91c8f6d351460239108bef5e7a0b6 ]
Since commit fa1f68db6ca7 ("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: 44b6b7661132 ("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 --- drivers/platform/x86/wmi.c | 20 ++++++-------------- 1 file changed, 6 insertions(+), 14 deletions(-)
diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c index 4b58590596184..136347a195ece 100644 --- a/drivers/platform/x86/wmi.c +++ b/drivers/platform/x86/wmi.c @@ -793,21 +793,13 @@ 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; - - 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; - } - } + /* + * 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);
- if (!filp->private_data) - return -ENODEV; + filp->private_data = wblock;
return nonseekable_open(inode, filp); }