linux-kernel - [PATCH 3.16.y-ckt 112/185] dell-laptop: Fix allocating & freeing SMI buffer page

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Message-Id: <1436951580-15977-113-git-send-email-luis.henriques@canonical.com>
Date:	Wed, 15 Jul 2015 10:11:47 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 112/185] dell-laptop: Fix allocating & freeing SMI buffer page

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@...il.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@...il.com>
Acked-by: Michal Hocko <mhocko@...e.cz>
Signed-off-by: Darren Hart <dvhart@...ux.intel.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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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