[PC-BSD Testing] acl_from_text leaking memory

Jim Wilcoxson prirun at gmail.com
Sun Nov 15 08:04:19 PST 2009


I've been working on a new backup program, HashBackup, and believe I
have found a memory leak with ACLs in PCBSD/FreeBSD 7.1 and OSX
(Leopard).

acl_from_text is a function that takes a text string as input, and
returns a pointer to a malloc'd acl.  This acl is then freed with
acl_free.  I noticed that acl_from_text appears to leak memory.  This
is not used during the backup of a filesystem, but is needed to do a
restore.

After looking at the acl_from_text source in /usr/src/lib/libc/posix1e
(from PCBSD7.1), I believe the problem is that the duplicate text
string, mybuf_p, is not freed on normal return of this function.  Here
is the end of this function:

        }

#if 0
        /* XXX Should we only return ACLs valid according to acl_valid? */
        /* Verify validity of the ACL we read in. */
        if (acl_valid(acl) == -1) {
                errno = EINVAL;
                goto error_label;
        }
#endif

        return(acl);

error_label:
        acl_free(acl);
        free(mybuf_p);
        return(NULL);
}

I think there should be a free(mybuf_p) before return(acl).

Here is a PCBSD/FreeBSD test program that causes the memory leak:

#include <stdio.h>
#include <sys/types.h>
#include <sys/acl.h>

main() {
   acl_t acl;
   char* acltext;

   acltext = "user::rw-\n group::r--\n mask::r--\n other::r--\n";
   while (1) {
      acl = acl_from_text(acltext);
      if (acl == NULL)
        printf("acl_from_text failed\n");
      if (acl_free(acl) != 0)
        printf("acl_free failed\n");
  }
}

I've subscribed to the lists for a few days in case there are
questions or I can help test something.

Thanks,
Jim
--
HashBackup beta: http://sites.google.com/site/hashbackup


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