none/tests/mmap_fcntl_bug.c

   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
  16 int 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 no one 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 }