1 files changed, 79 insertions, 4 deletions

diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
index 0624d1bd71b5..e3ce33a9954e 100644
--- a/tools/testing/selftests/vm/mremap_test.c
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -6,9 +6,11 @@
 
 #include <errno.h>
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
 #include <sys/mman.h>
 #include <time.h>
+#include <stdbool.h>
 
 #include "../kselftest.h"
 
@@ -65,6 +67,59 @@ enum {
 }
 
 /*
+ * Returns false if the requested remap region overlaps with an
+ * existing mapping (e.g text, stack) else returns true.
+ */
+static bool is_remap_region_valid(void *addr, unsigned long long size)
+{
+	void *remap_addr = NULL;
+	bool ret = true;
+
+	/* Use MAP_FIXED_NOREPLACE flag to ensure region is not mapped */
+	remap_addr = mmap(addr, size, PROT_READ | PROT_WRITE,
+					 MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
+					 -1, 0);
+
+	if (remap_addr == MAP_FAILED) {
+		if (errno == EEXIST)
+			ret = false;
+	} else {
+		munmap(remap_addr, size);
+	}
+
+	return ret;
+}
+
+/* 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.
  */
@@ -72,11 +127,18 @@ 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);
+					MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
+					-1, 0);
 	if (src_addr == MAP_FAILED) {
 		if (errno == EPERM || errno == EEXIST)
 			goto retry;
@@ -91,8 +153,10 @@ retry:
 	 * 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;
@@ -141,9 +205,20 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
 	if (!((unsigned long long) addr & c.dest_alignment))
 		addr = (void *) ((unsigned long long) addr | c.dest_alignment);
 
+	/* Don't destroy existing mappings unless expected to overlap */
+	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
+		/* Check for unsigned overflow */
+		if (addr + c.dest_alignment < addr) {
+			ksft_print_msg("Couldn't find a valid region to remap to\n");
+			ret = -1;
+			goto out;
+		}
+		addr += c.dest_alignment;
+	}
+
 	clock_gettime(CLOCK_MONOTONIC, &t_start);
 	dest_addr = mremap(src_addr, c.region_size, c.region_size,
-			MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
+					  MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
 	clock_gettime(CLOCK_MONOTONIC, &t_end);
 
 	if (dest_addr == MAP_FAILED) {