Re: [RFC] Bug in mkdir(2)
Kevin M. Bealer (kbealier@stny.lrun.com)
Fri, 02 Jul 1999 01:29:21 -0400
Alexander Viro wrote:
> Sigh... Looks like we got Yet Another Symlink Hole(tm). Not too
>serious one, since probably no suid-root stuff is perverted enough to
>trigger it, but anyway. Scenario:
>$ ln -sf b a
>$ ls -ld a b
>ls: b: No such file or directory
>lrwxrwxrwx 1 al al 1 Jun 16 12:56 a -> b
>$ mkdir a
>mkdir: cannot make directory `a': File exists
>$ mkdir a/
>$ ls -ld a b
>lrwxrwxrwx 1 al al 1 Jun 16 12:56 a -> b
>drwxrwxr-x 2 al al 1024 Jun 16 12:58 b
>
>In other words, if foo is a dangling symlink mkdir("foo/") will merrily
>follow it. Which it shouldn't.
>
>There are 3 reasonable variants of fix and they give different error
>values - -ENOENT (if we are treating it as a dangling link in the
>middle of lookup), -EEXIST (if we refuse to follow link here and ignore
>the trailing /) or -ENOTDIR (ditto, but noticed that it's not a
>directory). Take your pick ;-) Solaris prefers the second variant and IMO
>it's the right thing.
>
> BTW, rmdir("foo/") also shouldn't follow links. rmdir(1) works
>around that (it trims the trailing slashes), but IMHO rmdir(2) shold
>return -ENOTDIR here. Actually it happily follows the link.
>
> Patching it either way is fairly trivial and I'll submit the
>patches as soon as you will choose the variant. I think that the right
>thing to do here is to -EEXIST for mkdir() and -ENOTDIR for rmdir(). Up to
>you, indeed.
> Cheers,
> Al
>
>
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Just to add another data point (to a semi-old discussion), AIX
has the same behavior of mkdir("aardvark") fails for a symlink
and mkdir("aardvark/") follows the link.
-----kbealier.at.stny.lrun.com-------------------------------------
Probable-Possible, my black hen,
She lays eggs in the Relative When.
She doesn't lay eggs in the Positive Now
Because she's unable to postulate how.
-- Frederick Winsor
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