fedora 23
race weakness #34


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 23 race weakness.

 #   undef read
#   define read rpl_read
#  endif
_GL_FUNCDECL_RPL (read, ssize_t, (int fd, void *buf, size_t count)
                                 _GL_ARG_NONNULL ((2)));
_GL_CXXALIAS_RPL (read, ssize_t, (int fd, void *buf, size_t count));
# else
/* Need to cast, because on mingw, the third parameter is
                                                          unsigned int count
   and the return type is 'int'.  */
_GL_CXXALIAS_SYS_CAST (read, ssize_t, (int fd, void *buf, size_t count));
# endif

/* Read the contents of the symbolic link FILE and place the first BUFSIZE
   bytes of it into BUF.  Return the number of bytes placed into BUF if
   successful, otherwise -1 and errno set.
   See the POSIX:2008 specification
   <http://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html>.  */
#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
#   define readlink rpl_readlink
#  endif
_GL_FUNCDECL_RPL (readlink, ssize_t,
                  (const char *file, char *buf, size_t bufsize)
                  _GL_ARG_NONNULL ((1, 2)));
_GL_CXXALIAS_RPL (readlink, ssize_t,
                  (const char *file, char *buf, size_t bufsize));
# else
_GL_FUNCDECL_SYS (readlink, ssize_t,
                  (const char *file, char *buf, size_t bufsize)
                  _GL_ARG_NONNULL ((1, 2)));
#  endif
_GL_CXXALIAS_SYS (readlink, ssize_t,
                  (const char *file, char *buf, size_t bufsize));
# endif
_GL_CXXALIASWARN (readlink);
# undef readlink
_GL_WARN_ON_USE (readlink, "readlink is unportable - "
                 "use gnulib module readlink for portability");
# endif


The registered trademark Linux® is used pursuant to a sublicense from the Linux Foundation, the exclusive licensee of Linus Torvalds, owner of the mark on a world­wide basis.