[PATCH 3/4] dell-laptop: Fix allocating & freeing SMI buffer page

[Pali Rohár]

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.ro...@gmail.com>
---
 drivers/platform/x86/dell-laptop.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/platform/x86/dell-laptop.c 
b/drivers/platform/x86/dell-laptop.c
index aaef335..0a91599 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;
@@ -2097,12 +2096,11 @@ 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();
 
@@ -2165,7 +2163,7 @@ 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:
-- 
1.7.9.5

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