1 /*
2 * Copyright (C) 2012-2017 Red Hat, Inc.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
12 * the GNU General Public License for more details.
13 */
14
15 /* thp03 - Case for spliting unaligned memory.
16 * - System will panic if failed.
17 *
18 * Modified form a reproducer for
19 * https://patchwork.kernel.org/patch/1358441/
20 * Kernel Commit id: 027ef6c87853b0a9df53175063028edb4950d476
21 * There was a bug in THP, will crash happened due to the following
22 * reason according to developers:
23 *
24 * most VM places are using pmd_none but a few are still using
25 * pmd_present. The meaning is about the same for the pmd. However
26 * pmd_present would return the wrong value on PROT_NONE ranges or in
27 * case of a non reproducible race with split_huge_page.
28 * When the code using pmd_present gets a false negative, the kernel will
29 * crash. It's just an annoying DoS with a BUG_ON triggering: no memory
30 * corruption and no data corruption (nor userland nor kernel).
31 */
32
33 #include <sys/types.h>
34 #include <sys/wait.h>
35 #include <fcntl.h>
36 #include <stdlib.h>
37 #include <string.h>
38 #include <errno.h>
39 #include "mem.h"
40 #include "lapi/mmap.h"
41
42 static void thp_test(void);
43
44 static long hugepage_size;
45 static long unaligned_size;
46 static long page_size;
47
thp_test(void)48 static void thp_test(void)
49 {
50 void *p;
51
52 p = SAFE_MMAP(NULL, unaligned_size, PROT_READ | PROT_WRITE,
53 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
54
55 memset(p, 0x00, unaligned_size);
56 if (mprotect(p, unaligned_size, PROT_NONE) == -1)
57 tst_brk(TBROK | TERRNO, "mprotect");
58
59 if (madvise(p + hugepage_size, page_size, MADV_MERGEABLE) == -1) {
60 if (errno == EINVAL) {
61 tst_brk(TCONF,
62 "MADV_MERGEABLE is not enabled/supported");
63 } else {
64 tst_brk(TBROK | TERRNO, "madvise");
65 }
66 }
67
68 switch (SAFE_FORK()) {
69 case 0:
70 exit(0);
71 default:
72 SAFE_WAITPID(-1, NULL, 0);
73 }
74
75 tst_res(TPASS, "system didn't crash, pass.");
76 munmap(p, unaligned_size);
77 }
78
setup(void)79 static void setup(void)
80 {
81 if (access(PATH_THP, F_OK) == -1)
82 tst_brk(TCONF, "THP not enabled in kernel?");
83
84 check_hugepage();
85
86 hugepage_size = SAFE_READ_MEMINFO("Hugepagesize:") * KB;
87 unaligned_size = hugepage_size * 4 - 1;
88 page_size = SAFE_SYSCONF(_SC_PAGESIZE);
89 }
90
91 static struct tst_test test = {
92 .needs_root = 1,
93 .forks_child = 1,
94 .setup = setup,
95 .test_all = thp_test,
96 };
97