readlink in /proc w/ overlong path

readlink in /proc w/ overlong path

[Ulrich Drepper]

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Trying to read the overlong target of a /proc/*/fd/N file descriptor
leads with the current BK kernel to a segfault in the kernel.  This is
on x86 but I have no doubt it's a generaic error.  The following the
program illustrates the problem.

#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
int
main (void)
{
  const char s[] =
    "test_____________________________________________________________";
  int i;
  for (i = 0; i < 100; ++i)
    {
      mkdir (s, 0777);
      chdir (s);
    }
  int fd = open ("aaa", O_RDWR | O_CREAT);
  write (fd, "a", 1);
  char buf[200];
  sprintf (buf, "/proc/self/fd/%d", fd);
#define N 200000
  char *buf2 = (char *) malloc (N);
  if (buf2 == NULL)
    error (EXIT_FAILURE, errno, "failed to get memory");
  int n = readlink (buf, buf2, sizeof (buf2));
  if (n < 0 || n > N)
    printf ("readlink returned %d\n", n);
  else
    {
      buf2[n] = '\0';
      printf ("n = %d, %s\n", n, buf2);
    }
  return 0;
}


- -- 
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Ulrich Drepper \    ,-----------------'   \ Mountain View, CA 94041 USA
Red Hat         `--' drepper at redhat.com `---------------------------
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