1
2/* Test program to demonstrate valgrind breaking fcntl locks during
3 * mmap.  Feed it a r/w file, such as its own source code. */
4
5/* See bug 280965. */
6
7#include <stdio.h>
8#include <stdlib.h>
9#include <unistd.h>
10#include <fcntl.h>
11#include <sys/mman.h>
12#include <sys/types.h>
13#include <sys/wait.h>
14#include <err.h>
15
16int main(int argc, char *argv[])
17{
18	struct flock fl;
19	const char *file = /* argv[1]; */
20			   "mmap_fcntl_bug.c";
21	int fd, status;
22        off_t initial;
23
24	if (!file)
25		errx(1, "Usage: %s <normal-file>", argv[0]);
26
27	fd = open(file, O_RDWR);
28	if (fd < 0)
29		err(1, "Opening %s", file);
30
31        // reproduce bug 297991: mmap interferes with fd position
32        initial = lseek(fd, 123, SEEK_SET);
33        if (123 != initial)
34                err(1, "initial off_t differs from 123 (TEST FAILED)");
35        if (lseek(fd, 0, SEEK_CUR) != 123)
36                err(1, "zero offset from initial differs from 123 (TEST FAILED)");
37
38	fl.l_type = F_WRLCK;
39	fl.l_whence = SEEK_SET;
40	fl.l_start = 0;
41	fl.l_len = 1;
42
43	/* I'm assuming noone else tries to lock this! */
44	if (fcntl(fd, F_SETLK, &fl) != 0)
45		err(1, "Locking %s", file);
46
47	/* If under valgrind, mmap re-opens and closes file, screwing us */
48	if (mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0) == MAP_FAILED)
49		err(1, "mmap of %s", file);
50        if (lseek(fd, 0, SEEK_CUR) != 123)
51                errx(1, "zero offset from initial after mmap differs from 123 (TEST FAILED)");
52
53	switch (fork()) {
54	case 0:
55		/* Child.  Lock should fail. */
56		if (fcntl(fd, F_SETLK, &fl) == 0)
57			exit(1);
58		exit(0);
59	case -1:
60		err(1, "Fork failed");
61	}
62
63	if (wait(&status) == -1)
64		 err(1, "Child vanished?");
65
66	if (!WIFEXITED(status))
67		errx(1, "Child died with signal %i", WTERMSIG(status));
68
69	switch (WEXITSTATUS(status)) {
70	case 1:
71		errx(1, "Child got lock, we must have dropped it (TEST FAILED)");
72	case 0:
73		fprintf(stderr, "Child exited with zero (TEST PASSED).\n");
74		return 0;
75	default:
76		errx(1, "Child weird exit status %i", WEXITSTATUS(status));
77	}
78}
79