fedora 24
race weakness #9


Weakness Breakdown


A race condition exists when parallel code accesses shared data without proper coordination. An attack that uses a race-condition weakness takes advantage of the unsafe data access to manipulate how one of the parallel sections of code reacts. Even though each process runs as intended, the outcome is unexpected. For example, consider a bank service that depends on an encryption key that it reads from a known location. An independent cryptography service is responsible for generating the key and placing it where the bank is expected to read it in a timely manner. If the bank and cryptography services do not coordinate with each other, then the bank may read a blank encryption key before cryptography writes the key to the location. This can effectively turn off all encryption for the bank without either service, or the administrator, knowing that something has gone wrong.

Warning code(s):

This accepts filename arguments; if an attacker can move those files or change the link content, a race condition results. Also, it does not terminate with ASCII NUL..

File Name:



The highlighted line of code below is the trigger point of this particular Fedora 24 race weakness.

  *  but WITHOUT ANY WARRANTY; without even the implied warranty of          *
 *  GNU Lesser General Public License for more details.                     *
 *                                                                          *
 *  You should have received a copy of the GNU Lesser General Public        *
 *  License along with DMTCP:dmtcp/src.  If not, see                        *
 *  <http://www.gnu.org/licenses/>.                                         *

/* realpath is defined with "always_inline" attribute. GCC>=4.7 disallows us
 * to define the realpath wrapper if compiled with -O0. Here we are renaming
 * realpath so that later code does not see the declaration of realpath as
 * inline. Normal user code from other files will continue to invoke realpath
 * as an inline function calling __ptsname_r_chk. Later in this file
 * we define __ptsname_r_chk to call the original realpath symbol.
 * Similarly, for ttyname_r, etc.
 * Also, on some machines (e.g. SLES 10), readlink has conflicting return types
 * (ssize_t and int).
 *     In general, we rename the functions below, since any type declarations
 * may vary on different systems, and so we ignore these type declarations.
#define open open_always_inline
#define open64 open64_always_inline
#define readlink readlink_always_inline
#define realpath realpath_always_inline

#include <stdio.h>
#include <stdarg.h>
#include <sys/ioctl.h>
#include <string.h>

#undef open
#undef open64
#undef readlink
#undef realpath

#include "jassert.h"
#include "jfilesystem.h"
#include "jconvert.h"
#include "pidwrappers.h"
#include "util.h"
#include "virtualpidtable.h"
#include "dmtcp.h"
#include "pid.h"

#define PROC_PREFIX "/proc/"

using namespace dmtcp;

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