CVS coreutils now uses <sys/fcntl.h>'s O_NOFOLLOW, when available, to avoid a data race when changing directories while avoiding symlinks (necessary for some traversal algorithms). Normally, calling lstat() to prove something is a directory, followed by chdir(), is a security risk, since lstat() could see a directory, then the attacker replaces the directory with a symlink, so that the program then changes to the wrong directory. But on platforms like newer Linux where O_NOFOLLOW causes open() to fail when opening symlinks, the sequence open(), fstat(), fchdir(), close() avoids the race by proving that the target is still a directory and has not been replaced by a symlink at the last minute.
It seems like it might be easy to add an O_NOFOLLOW flag to cygwin (perhaps post-1.5.19), especially since you recently added O_*SYNC and O_DIRECT. But I don't have copyright papers in place, so for now this is just a feature request that you are free to ignore, until someone provides an actual patch. -- Eric Blake -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
