[PATCH 5.15 138/177] selftest/vm: verify mmap addr in mremap_test

Greg Kroah-Hartman
2022-05-04T17:24:18Z

From: Sidhartha Kumar <sidhartha.kumar@oracle.com>

[ Upstream commit 9c85a9bae267f6b5e5e374d0d023bbbe9db096d3 ]

Avoid calling mmap with requested addresses that are less than the
system's mmap_min_addr. When run as root, mmap returns EACCES when
trying to map addresses < mmap_min_addr. This is not one of the error
codes for the condition to retry the mmap in the test.

Rather than arbitrarily retrying on EACCES, don't attempt an mmap until
addr > vm.mmap_min_addr.

Add a munmap call after an alignment check as the mappings are retained
after the retry and can reach the vm.max_map_count sysctl.

Link: https://lkml.kernel.org/r/20220420215721.4868-1-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/vm/mremap_test.c | 41 +++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
index 0624d1bd71b5..2b3b4f15185f 100644
--- a/tools/testing/selftests/vm/mremap_test.c
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -6,6 +6,7 @@

#include <errno.h>
#include <stdlib.h>
+#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <time.h>
@@ -64,6 +65,35 @@ enum {
.expect_failure = should_fail \
}

+/* Returns mmap_min_addr sysctl tunable from procfs */
+static unsigned long long get_mmap_min_addr(void)
+{
+ FILE *fp;
+ int n_matched;
+ static unsigned long long addr;
+
+ if (addr)
+ return addr;
+
+ fp = fopen("/proc/sys/vm/mmap_min_addr", "r");
+ if (fp == NULL) {
+ ksft_print_msg("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
+ strerror(errno));
+ exit(KSFT_SKIP);
+ }
+
+ n_matched = fscanf(fp, "%llu", &addr);
+ if (n_matched != 1) {
+ ksft_print_msg("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
+ strerror(errno));
+ fclose(fp);
+ exit(KSFT_SKIP);
+ }
+
+ fclose(fp);
+ return addr;
+}
+
/*
* Returns the start address of the mapping on success, else returns
* NULL on failure.
@@ -72,8 +102,15 @@ static void *get_source_mapping(struct config c)
{
unsigned long long addr = 0ULL;
void *src_addr = NULL;
+ unsigned long long mmap_min_addr;
+
+ mmap_min_addr = get_mmap_min_addr();
+
retry:
addr += c.src_alignment;
+ if (addr < mmap_min_addr)
+ goto retry;
+
src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
-1, 0);
@@ -91,8 +128,10 @@ static void *get_source_mapping(struct config c)
* alignment in the tests.
*/
if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
- !((unsigned long long) src_addr & c.src_alignment))
+ !((unsigned long long) src_addr & c.src_alignment)) {
+ munmap(src_addr, c.region_size);
goto retry;
+ }

if (!src_addr)
goto error;
--
2.35.1