dell-laptop: Fix allocating & freeing SMI buffer page

commit b8830a4e71b15d0364ac8e6c55301eea73f211da upstream.

This commit fix kernel crash when probing for rfkill devices in dell-laptop
driver failed. Function free_page() was incorrectly used on struct page *
instead of virtual address of SMI buffer.

This commit also simplify allocating page for SMI buffer by using
__get_free_page() function instead of sequential call of functions
alloc_page() and page_address().

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index d688d80..2c1d5f5 100644 (file)
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -305,7 +305,6 @@ static const struct dmi_system_id dell_quirks[] __initconst = {
 };
 
 static struct calling_interface_buffer *buffer;
-static struct page *bufferpage;
 static DEFINE_MUTEX(buffer_mutex);
 
 static int hwswitch_state;
@@ -1896,12 +1895,11 @@ static int __init dell_init(void)
         * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
         * is passed to SMI handler.
         */
-       bufferpage = alloc_page(GFP_KERNEL | GFP_DMA32);
-       if (!bufferpage) {
+       buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
+       if (!buffer) {
                ret = -ENOMEM;
                goto fail_buffer;
        }
-       buffer = page_address(bufferpage);
 
        ret = dell_setup_rfkill();
 
@@ -1965,7 +1963,7 @@ fail_backlight:
        cancel_delayed_work_sync(&dell_rfkill_work);
        dell_cleanup_rfkill();
 fail_rfkill:
-       free_page((unsigned long)bufferpage);
+       free_page((unsigned long)buffer);
 fail_buffer:
        platform_device_del(platform_device);
 fail_platform_device2: