linux-kernel - [PATCH] mmc: mmc_test: Fix NULL dereference on allocation failure

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Message-ID: <8c90be28-67b4-4b0d-a105-034dc72a0b31@stanley.mountain>
Date: Tue, 20 Aug 2024 11:44:08 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Pierre Ossman <drzeus@...eus.cx>
Cc: Ulf Hansson <ulf.hansson@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] mmc: mmc_test: Fix NULL dereference on allocation failure

If the "test->highmem = alloc_pages()" allocation fails then calling
__free_pages(test->highmem) will result in a NULL dereference.  Also
change the error code to -ENOMEM instead of returning success.

Fixes: 2661081f5ab9 ("mmc_test: highmem tests")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
This code is from 2008 so it must not be that much of an issue in real
life.

 drivers/mmc/core/mmc_test.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/core/mmc_test.c b/drivers/mmc/core/mmc_test.c
index 8f7f587a0025..b7f627a9fdea 100644
--- a/drivers/mmc/core/mmc_test.c
+++ b/drivers/mmc/core/mmc_test.c
@@ -3125,13 +3125,13 @@ static ssize_t mtf_test_write(struct file *file, const char __user *buf,
 	test->buffer = kzalloc(BUFFER_SIZE, GFP_KERNEL);
 #ifdef CONFIG_HIGHMEM
 	test->highmem = alloc_pages(GFP_KERNEL | __GFP_HIGHMEM, BUFFER_ORDER);
+	if (!test->highmem) {
+		count = -ENOMEM;
+		goto free_test_buffer;
+	}
 #endif
 
-#ifdef CONFIG_HIGHMEM
-	if (test->buffer && test->highmem) {
-#else
 	if (test->buffer) {
-#endif
 		mutex_lock(&mmc_test_lock);
 		mmc_test_run(test, testcase);
 		mutex_unlock(&mmc_test_lock);
@@ -3139,6 +3139,7 @@ static ssize_t mtf_test_write(struct file *file, const char __user *buf,
 
 #ifdef CONFIG_HIGHMEM
 	__free_pages(test->highmem, BUFFER_ORDER);
+free_test_buffer:
 #endif
 	kfree(test->buffer);
 	kfree(test);
-- 
2.43.0