linux-kernel - [PATCH] selftests/mm: compaction_test: Fix off by one in check

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Message-ID: <87470c06-b45a-4e83-92ff-aac2e7b9c6ba@stanley.mountain>
Date: Fri, 9 Aug 2024 15:32:30 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Dev Jain <dev.jain@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Shuah Khan <shuah@...nel.org>, linux-mm@...ck.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH] selftests/mm: compaction_test: Fix off by one in
 check_compaction()

The "initial_nr_hugepages" variable is unsigned long so it takes up to
20 characters to print, plus 1 more character for the NUL terminator.
Unfortunately, this buffer is not quite large enough for the terminator
to fit.  Also use snprintf() for a belt and suspenders approach.

Fixes: fb9293b6b015 ("selftests/mm: compaction_test: fix bogus test success and reduce probability of OOM-killer invocation")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 tools/testing/selftests/mm/compaction_test.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
index e140558e6f53..2c3a0eb6b22d 100644
--- a/tools/testing/selftests/mm/compaction_test.c
+++ b/tools/testing/selftests/mm/compaction_test.c
@@ -89,9 +89,10 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size,
 	int fd, ret = -1;
 	int compaction_index = 0;
 	char nr_hugepages[20] = {0};
-	char init_nr_hugepages[20] = {0};
+	char init_nr_hugepages[24] = {0};
 
-	sprintf(init_nr_hugepages, "%lu", initial_nr_hugepages);
+	snprintf(init_nr_hugepages, sizeof(init_nr_hugepages),
+		 "%lu", initial_nr_hugepages);
 
 	/* We want to test with 80% of available memory. Else, OOM killer comes
 	   in to play */
-- 
2.43.0