[PATCH 3.2 049/110] dell-laptop: Fix allocating & freeing SMI buffer page

From: Ben Hutchings
Date: Mon Aug 10 2015 - 06:18:38 EST

3.2.71-rc1 review patch. If anyone has any objections, please let me know.


From: Pali RohÃr <pali.rohar@xxxxxxxxx>

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 RohÃr <pali.rohar@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
drivers/platform/x86/dell-laptop.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -215,7 +215,6 @@ static struct dmi_system_id __devinitdat

static struct calling_interface_buffer *buffer;
-static struct page *bufferpage;
static DEFINE_MUTEX(buffer_mutex);

static int hwswitch_state;
@@ -715,11 +714,10 @@ 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);
+ buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);

- if (!bufferpage)
+ if (!buffer)
goto fail_buffer;
- buffer = page_address(bufferpage);

ret = dell_setup_rfkill();

@@ -788,7 +786,7 @@ fail_backlight:
- free_page((unsigned long)bufferpage);
+ free_page((unsigned long)buffer);

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