linux-kernel - [PATCH] platform/x86: wmi: Do not mix pages and kmalloc

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Message-ID: <20180620213141.GA8957@beast>
Date:   Wed, 20 Jun 2018 14:31:41 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Darren Hart <dvhart@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org,
        Mihai Donțu <mihai.dontu@...il.com>,
        Mario.Limonciello@...l.com
Subject: [PATCH] platform/x86: wmi: Do not mix pages and kmalloc

The probe handler_data was being allocated with __get_free_pages()
for no reason I could find. The error path was using kfree(). Since
other things are happily using kmalloc() in the probe path, switch to
kmalloc() entirely. This fixes the error path mismatch and will avoid
issues with CONFIG_HARDENED_USERCOPY_PAGESPAN=y.

Reported-by: Mihai Donțu <mihai.dontu@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/platform/x86/wmi.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index 8e3d0146ff8c..04791ea5d97b 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -895,7 +895,6 @@ static int wmi_dev_probe(struct device *dev)
 	struct wmi_driver *wdriver =
 		container_of(dev->driver, struct wmi_driver, driver);
 	int ret = 0;
-	int count;
 	char *buf;
 
 	if (ACPI_FAILURE(wmi_method_enable(wblock, 1)))
@@ -917,9 +916,8 @@ static int wmi_dev_probe(struct device *dev)
 			goto probe_failure;
 		}
 
-		count = get_order(wblock->req_buf_size);
-		wblock->handler_data = (void *)__get_free_pages(GFP_KERNEL,
-								count);
+		wblock->handler_data = kmalloc(wblock->req_buf_size,
+					       GFP_KERNEL);
 		if (!wblock->handler_data) {
 			ret = -ENOMEM;
 			goto probe_failure;
@@ -964,8 +962,7 @@ static int wmi_dev_remove(struct device *dev)
 	if (wdriver->filter_callback) {
 		misc_deregister(&wblock->char_dev);
 		kfree(wblock->char_dev.name);
-		free_pages((unsigned long)wblock->handler_data,
-			   get_order(wblock->req_buf_size));
+		kfree(wblock->handler_data);
 	}
 
 	if (wdriver->remove)
-- 
2.17.1


-- 
Kees Cook
Pixel Security