linux-kernel - [PATCH] dell-laptop: Fix allocating & freeing SMI buffer page

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Message-Id: <1435047079-949-1-git-send-email-pali.rohar@gmail.com>
Date:	Tue, 23 Jun 2015 10:11:19 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Darren Hart <dvhart@...radead.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Michal Hocko <mhocko@...e.cz>
Cc:	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Pali Rohár <pali.rohar@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH] 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@...il.com>
Acked-by: Michal Hocko <mhocko@...e.cz>
Cc: stable@...r.kernel.org
---
 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 d688d80..2c1d5f5 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -305,7 +305,6 @@ 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;
@@ -1896,12 +1895,11 @@ 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();
 
@@ -1965,7 +1963,7 @@ 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:
-- 
1.7.10.4

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