[PATCH 5.15 42/59] selftests: secretmem: floor the memory size to the multiple of page_size

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>

[ Upstream commit 0aac13add26d546ac74c89d2883b3a5f0fbea039 ]

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.

This was getting triggered on KernelCI regularly because of different
ulimit settings which wasn't multiple of the page_size.  Find logs
here: https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/
The bug in was present from the time test was first added.

Link: https://lkml.kernel.org/r/20231214101931.1155586-1-usama.anjum@xxxxxxxxxxxxx
Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Reported-by: "kernelci.org bot" <bot@xxxxxxxxxxxx>
Closes: https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/
Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/testing/selftests/vm/memfd_secret.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/vm/memfd_secret.c b/tools/testing/selftests/vm/memfd_secret.c
index 93e7e7ffed337..9177490981489 100644
--- a/tools/testing/selftests/vm/memfd_secret.c
+++ b/tools/testing/selftests/vm/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");
-- 
2.43.0







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