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Subject[PATCH 3.16.y-ckt 112/185] dell-laptop: Fix allocating & freeing SMI buffer page
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3.16.7-ckt15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali.rohar@gmail.com>

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: Luis Henriques <luis.henriques@canonical.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 fed4111ac31a..1beb232ef03b 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -272,7 +272,6 @@ static struct dmi_system_id dell_quirks[] = {
};

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

static int hwswitch_state;
@@ -825,12 +824,11 @@ 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();

@@ -892,7 +890,7 @@ 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:

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