Re: [PATCH] selftests/vm: Add a test for MAP_FIXED_NOREPLACE

From: Kees Cook
Date: Sat Oct 13 2018 - 21:17:04 EST

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On Sat, Oct 13, 2018 at 6:39 AM, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
> Add a test for MAP_FIXED_NOREPLACE, based on some code originally by
> Jann Horn. This would have caught the overlap bug reported by Daniel Micay.
>
> I originally suggested to Michal that we create MAP_FIXED_NOREPLACE, but
> instead of writing a selftest I spent my time bike-shedding whether it
> should be called MAP_FIXED_SAFE/NOCLOBBER/WEAK/NEW .. mea culpa.

LOL. :)

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

>
> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> ---
> tools/testing/selftests/vm/.gitignore | 1 +
> tools/testing/selftests/vm/Makefile | 1 +
> .../selftests/vm/map_fixed_noreplace.c | 206 ++++++++++++++++++
> 3 files changed, 208 insertions(+)
> create mode 100644 tools/testing/selftests/vm/map_fixed_noreplace.c
>
> diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
> index af5ff83f6d7f..31b3c98b6d34 100644
> --- a/tools/testing/selftests/vm/.gitignore
> +++ b/tools/testing/selftests/vm/.gitignore
> @@ -13,3 +13,4 @@ mlock-random-test
> virtual_address_range
> gup_benchmark
> va_128TBswitch
> +map_fixed_noreplace
> diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
> index e94b7b14bcb2..6e67e726e5a5 100644
> --- a/tools/testing/selftests/vm/Makefile
> +++ b/tools/testing/selftests/vm/Makefile
> @@ -12,6 +12,7 @@ TEST_GEN_FILES += gup_benchmark
> TEST_GEN_FILES += hugepage-mmap
> TEST_GEN_FILES += hugepage-shm
> TEST_GEN_FILES += map_hugetlb
> +TEST_GEN_FILES += map_fixed_noreplace
> TEST_GEN_FILES += map_populate
> TEST_GEN_FILES += mlock-random-test
> TEST_GEN_FILES += mlock2-tests
> diff --git a/tools/testing/selftests/vm/map_fixed_noreplace.c b/tools/testing/selftests/vm/map_fixed_noreplace.c
> new file mode 100644
> index 000000000000..d91bde511268
> --- /dev/null
> +++ b/tools/testing/selftests/vm/map_fixed_noreplace.c
> @@ -0,0 +1,206 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Test that MAP_FIXED_NOREPLACE works.
> + *
> + * Copyright 2018, Jann Horn <jannh@xxxxxxxxxx>
> + * Copyright 2018, Michael Ellerman, IBM Corporation.
> + */
> +
> +#include <sys/mman.h>
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +
> +#ifndef MAP_FIXED_NOREPLACE
> +#define MAP_FIXED_NOREPLACE 0x100000
> +#endif
> +
> +#define BASE_ADDRESS (256ul * 1024 * 1024)
> +
> +
> +static void dump_maps(void)
> +{
> + char cmd[32];
> +
> + snprintf(cmd, sizeof(cmd), "cat /proc/%d/maps", getpid());
> + system(cmd);
> +}
> +
> +int main(void)
> +{
> + unsigned long flags, addr, size, page_size;
> + char *p;
> +
> + page_size = sysconf(_SC_PAGE_SIZE);
> +
> + flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE;
> +
> + // Check we can map all the areas we need below
> + errno = 0;
> + addr = BASE_ADDRESS;
> + size = 5 * page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> +
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p == MAP_FAILED) {
> + dump_maps();
> + printf("Error: couldn't map the space we need for the test\n");
> + return 1;
> + }
> +
> + errno = 0;
> + if (munmap((void *)addr, 5 * page_size) != 0) {
> + dump_maps();
> + printf("Error: munmap failed!?\n");
> + return 1;
> + }
> + printf("unmap() successful\n");
> +
> + errno = 0;
> + addr = BASE_ADDRESS + page_size;
> + size = 3 * page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p == MAP_FAILED) {
> + dump_maps();
> + printf("Error: first mmap() failed unexpectedly\n");
> + return 1;
> + }
> +
> + /*
> + * Exact same mapping again:
> + * base | free | new
> + * +1 | mapped | new
> + * +2 | mapped | new
> + * +3 | mapped | new
> + * +4 | free | new
> + */
> + errno = 0;
> + addr = BASE_ADDRESS;
> + size = 5 * page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p != MAP_FAILED) {
> + dump_maps();
> + printf("Error:1: mmap() succeeded when it shouldn't have\n");
> + return 1;
> + }
> +
> + /*
> + * Second mapping contained within first:
> + *
> + * base | free |
> + * +1 | mapped |
> + * +2 | mapped | new
> + * +3 | mapped |
> + * +4 | free |
> + */
> + errno = 0;
> + addr = BASE_ADDRESS + (2 * page_size);
> + size = page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p != MAP_FAILED) {
> + dump_maps();
> + printf("Error:2: mmap() succeeded when it shouldn't have\n");
> + return 1;
> + }
> +
> + /*
> + * Overlap end of existing mapping:
> + * base | free |
> + * +1 | mapped |
> + * +2 | mapped |
> + * +3 | mapped | new
> + * +4 | free | new
> + */
> + errno = 0;
> + addr = BASE_ADDRESS + (3 * page_size);
> + size = 2 * page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p != MAP_FAILED) {
> + dump_maps();
> + printf("Error:3: mmap() succeeded when it shouldn't have\n");
> + return 1;
> + }
> +
> + /*
> + * Overlap start of existing mapping:
> + * base | free | new
> + * +1 | mapped | new
> + * +2 | mapped |
> + * +3 | mapped |
> + * +4 | free |
> + */
> + errno = 0;
> + addr = BASE_ADDRESS;
> + size = 2 * page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p != MAP_FAILED) {
> + dump_maps();
> + printf("Error:4: mmap() succeeded when it shouldn't have\n");
> + return 1;
> + }
> +
> + /*
> + * Adjacent to start of existing mapping:
> + * base | free | new
> + * +1 | mapped |
> + * +2 | mapped |
> + * +3 | mapped |
> + * +4 | free |
> + */
> + errno = 0;
> + addr = BASE_ADDRESS;
> + size = page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p == MAP_FAILED) {
> + dump_maps();
> + printf("Error:5: mmap() failed when it shouldn't have\n");
> + return 1;
> + }
> +
> + /*
> + * Adjacent to end of existing mapping:
> + * base | free |
> + * +1 | mapped |
> + * +2 | mapped |
> + * +3 | mapped |
> + * +4 | free | new
> + */
> + errno = 0;
> + addr = BASE_ADDRESS + (4 * page_size);
> + size = page_size;
> + p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
> + printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
> +
> + if (p == MAP_FAILED) {
> + dump_maps();
> + printf("Error:6: mmap() failed when it shouldn't have\n");
> + return 1;
> + }
> +
> + addr = BASE_ADDRESS;
> + size = 5 * page_size;
> + if (munmap((void *)addr, size) != 0) {
> + dump_maps();
> + printf("Error: munmap failed!?\n");
> + return 1;
> + }
> + printf("unmap() successful\n");
> +
> + printf("OK\n");
> + return 0;
> +}
> --
> 2.17.1
>

--
Kees Cook
Pixel Security

Next message: Miss Juliet Muhammad: "Urgent,"
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In reply to: Michael Ellerman: "[PATCH] selftests/vm: Add a test for MAP_FIXED_NOREPLACE"
Next in thread: Khalid Aziz: "Re: [PATCH] selftests/vm: Add a test for MAP_FIXED_NOREPLACE"
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