Commit 9c85a9ba authored by Sidhartha Kumar's avatar Sidhartha Kumar Committed by Linus Torvalds
Browse files

selftest/vm: verify mmap addr in mremap_test 

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: default avatarSidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: default avatarShuah Khan <skhan@linuxfoundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5f24d5a5

tools/testing/selftests/vm/mremap_test.c

+40 −1
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 


#include <errno.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <sys/mman.h>

#include <time.h>
@@ -63,6 +64,35 @@ 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.
@@ -71,8 +101,15 @@ 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);
@@ -90,8 +127,10 @@ 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;