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.
This accepts filename arguments; if an attacker can move those files, a race condition results..
The highlighted line of code below is the trigger point of this particular Centos 7 race weakness.
# if @HAVE_FUTIMENS@ _GL_CXXALIASWARN (futimens); # endif #elif defined GNULIB_POSIXCHECK # undef futimens # if HAVE_RAW_DECL_FUTIMENS _GL_WARN_ON_USE (futimens, "futimens is not portable - " "use gnulib module futimens for portability"); # endif #endif #if @GNULIB_LCHMOD@ /* Change the mode of FILENAME to MODE, without dereferencing it if FILENAME denotes a symbolic link. */ # if !@HAVE_LCHMOD@ /* The lchmod replacement follows symbolic links. Callers should take this into account; lchmod should be applied only to arguments that are known to not be symbolic links. On hosts that lack lchmod, this can lead to race conditions between the check and the invocation of lchmod, but we know of no workarounds that are reliable in general. You might try requesting support for lchmod from your operating system supplier. */ # if !(defined __cplusplus && defined GNULIB_NAMESPACE) # define lchmod chmod # endif /* Need to cast, because on mingw, the second parameter of chmod is int mode. */ _GL_CXXALIAS_RPL_CAST_1 (lchmod, chmod, int, (const char *filename, mode_t mode)); # else # if 0 /* assume already declared */ _GL_FUNCDECL_SYS (lchmod, int, (const char *filename, mode_t mode) _GL_ARG_NONNULL ((1))); # endif _GL_CXXALIAS_SYS (lchmod, int, (const char *filename, mode_t mode)); # endif # if @HAVE_LCHMOD@ _GL_CXXALIASWARN (lchmod); # endif #elif defined GNULIB_POSIXCHECK # undef lchmod # if HAVE_RAW_DECL_LCHMOD _GL_WARN_ON_USE (lchmod, "lchmod is unportable - " "use gnulib module lchmod for portability"); # endif #endif #if @GNULIB_LSTAT@