selftest/vm: verify mmap addr in mremap_test

[ 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>

diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
index e3ce33a..efcbf53 100644 (file)
--- a/tools/testing/selftests/vm/mremap_test.c
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -66,6 +66,35 @@ 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 false if the requested remap region overlaps with an
  * existing mapping (e.g text, stack) else returns true.