linux-kernel - [PATCH] selftests/vm: Fix map_hugetlb length used for testing read and write

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Message-Id: <9a404a13c871c4bd0ba9ede68f69a1225180dd7e.1580978385.git.christophe.leroy@c-s.fr>
Date:   Thu,  6 Feb 2020 08:42:00 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Shuah Khan <shuah@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: [PATCH] selftests/vm: Fix map_hugetlb length used for testing read
 and write

Commit fa7b9a805c79 ("tools/selftest/vm: allow choosing mem size and
page size in map_hugetlb") added the possibility to change the size
of memory mapped for the test, but left the read and write test using
the default value. This is unnoticed when mapping a length greater
than the default one, but segfaults otherwise.

Fix read_bytes() and write_bytes() by giving them the real length.

Also fix the call to munmap().

Fixes: fa7b9a805c79 ("tools/selftest/vm: allow choosing mem size and page size in map_hugetlb")
Cc: stable@...r.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 tools/testing/selftests/vm/map_hugetlb.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/vm/map_hugetlb.c b/tools/testing/selftests/vm/map_hugetlb.c
index 5a2d7b8efc40..6af951900aa3 100644
--- a/tools/testing/selftests/vm/map_hugetlb.c
+++ b/tools/testing/selftests/vm/map_hugetlb.c
@@ -45,20 +45,20 @@ static void check_bytes(char *addr)
 	printf("First hex is %x\n", *((unsigned int *)addr));
 }
 
-static void write_bytes(char *addr)
+static void write_bytes(char *addr, size_t length)
 {
 	unsigned long i;
 
-	for (i = 0; i < LENGTH; i++)
+	for (i = 0; i < length; i++)
 		*(addr + i) = (char)i;
 }
 
-static int read_bytes(char *addr)
+static int read_bytes(char *addr, size_t length)
 {
 	unsigned long i;
 
 	check_bytes(addr);
-	for (i = 0; i < LENGTH; i++)
+	for (i = 0; i < length; i++)
 		if (*(addr + i) != (char)i) {
 			printf("Mismatch at %lu\n", i);
 			return 1;
@@ -96,11 +96,11 @@ int main(int argc, char **argv)
 
 	printf("Returned address is %p\n", addr);
 	check_bytes(addr);
-	write_bytes(addr);
-	ret = read_bytes(addr);
+	write_bytes(addr, length);
+	ret = read_bytes(addr, length);
 
 	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
-	if (munmap(addr, LENGTH)) {
+	if (munmap(addr, length)) {
 		perror("munmap");
 		exit(1);
 	}
-- 
2.25.0