I've been looking into that, and my head hurts. It looks too simple, so I'm
sure I'm reading it wrong.
What does the LOOKUP_FOLLOW flag to lookup_dentry() do?
open_namei() seems to call lookup_dentry() with LOOKUP_FOLLOW set by default,
unless the flags passed to open_namei() include O_CREAT and O_EXCL...
* Special case: O_CREAT|O_EXCL on a dangling symlink should
* give EEXIST for security reasons. While inconsistent, this
* is the same scheme used by, for example, Solaris 2.5.1. --KAB
dentry = lookup_dentry(pathname, NULL,
(flag & (O_CREAT|O_EXCL)) != (O_CREAT|O_EXCL));
So what happens if I add a new flags O_NOFOLLOW, and make open_namei clear the
LOOKUP_FOLLOW bit when O_NOFOLLOW is set?
Judging by the comment extracted above, it'll behave correctly for the
dangling symlink case, but not when the symlink points to a real file.
I suppose I should just try it.
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