linux-kernel - [PATCH] selftests: secretmem: Floor the memory size to the multiple of page

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Message-ID: <20231214101931.1155586-1-usama.anjum@collabora.com>
Date:   Thu, 14 Dec 2023 15:19:30 +0500
From:   Muhammad Usama Anjum <usama.anjum@...labora.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        James Bottomley <James.Bottomley@...senPartnership.com>
Cc:     Muhammad Usama Anjum <usama.anjum@...labora.com>,
        kernel@...labora.com, "kernelci.org bot" <bot@...nelci.org>,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] selftests: secretmem: Floor the memory size to the multiple of page_size

The "locked-in-memory size" limit per process can be non-multiple of
page_size. The mmap() fails if we try to allocate locked-in-memory
with same size as the allowed limit if it isn't multiple of the
page_size because mmap() rounds off the memory size to be allocated
to next multiple of page_size.

Fix this by flooring the length to be allocated with mmap() to the
previous multiple of the page_size.

Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)")
Reported-by: "kernelci.org bot" <bot@...nelci.org>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
---
 tools/testing/selftests/mm/memfd_secret.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/mm/memfd_secret.c b/tools/testing/selftests/mm/memfd_secret.c
index 957b9e18c729..9b298f6a04b3 100644
--- a/tools/testing/selftests/mm/memfd_secret.c
+++ b/tools/testing/selftests/mm/memfd_secret.c
@@ -62,6 +62,9 @@ static void test_mlock_limit(int fd)
 	char *mem;
 
 	len = mlock_limit_cur;
+	if (len % page_size != 0)
+		len = (len/page_size) * page_size;
+
 	mem = mmap(NULL, len, prot, mode, fd, 0);
 	if (mem == MAP_FAILED) {
 		fail("unable to mmap secret memory\n");
-- 
2.42.0