dell-laptop: Fix allocating & freeing SMI buffer page

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>
Cc: stable@vger.kernel.org
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index 9724613c28a6..35758cbc6bc8 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -306,7 +306,6 @@ 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;
@@ -2068,12 +2067,11 @@ 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();
 
@@ -2135,7 +2133,7 @@ static int __init dell_init(void)
 fail_backlight:
         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: