On 06/13/2013 10:22 AM, Thomas Rast wrote: > Michael Haggerty <mhag...@alum.mit.edu> writes: > >> One race is still possible and undetected: another process could >> change the file from a regular file into a symlink between the call to >> lstat and the call to open(). The open() call would silently follow >> the symlink and not know that something is wrong. I don't see a way >> to detect this situation without the use of the O_NOFOLLOW option, >> which is not portable and is not used elsewhere in our code base. >> >> However, we don't use symlinks anymore, so this situation is unlikely. >> And it doesn't appear that treating a symlink as a regular file would >> have grave consequences; after all, this is exactly how the code >> handles non-relative symlinks. > > You could fstat() the fd you got from open(), and verify that it is > still the same inode/device. That's wasting one syscall per ref for > pretty much everyone, but perhaps if we really cared about this (and I > gather from the above that we don't), we could conditionally use > O_NOFOLLOW if available, otherwise do that fstat().
Yes, that would work. For now I think I will not worry about it, but I'll keep your trick in mind. Thanks, Michael -- Michael Haggerty mhag...@alum.mit.edu http://softwareswirl.blogspot.com/ -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
