rmdir(2) and mkdir(2) both return EISDIR for argument "/"

[Alexander Best]

Gary Jennejohn schrieb am 2009-11-06:
> On Fri, 06 Nov 2009 17:43:06 +0100 (CET)
> Alexander Best <alexbestms at math.uni-muenster.de> wrote:

> > Gary Jennejohn schrieb am 2009-11-06:
> > > On Fri, 06 Nov 2009 16:32:22 +0100 (CET)
> > > Alexander Best <alexbestms at math.uni-muenster.de> wrote:

> > > > Alex Dupre schrieb am 2009-11-06:
> > > > > Alexander Best ha scritto:
> > > > > > i dug up this old pr
> > > > > > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/59739

> > > > > I think the EISDIR error is coming from kern/vfs_lookup.c,
> > > > > lookup()
> > > > > function with cn_nameptr = "":


> > > > >         /*
> > > > >          * Check for degenerate name (e.g. / or "")
> > > > >          * which is a way of talking about a directory,
> > > > >          * e.g. like "/." or ".".
> > > > >          */
> > > > >         if (cnp->cn_nameptr[0] == '\0') {
> > > > >                 ...
> > > > >                 if (cnp->cn_nameiop != LOOKUP) {
> > > > >                         error = EISDIR;
> > > > >                         goto bad;
> > > > >                 }
> > > > >                 ...

> > > > thanks a lot for finding the problem in the src. what do you
> > > > think
> > > > of the
> > > > patch attached to this message? after applying it the example
> > > > code
> > > > i posted in
> > > > my previous message returns the following output (instead of
> > > > EISDIR):

> > > > rmdir errno: 16 (which is EBUSY)
> > > > mkdir errno: 17 (which is EEXIST)

> > > > i don't know if these really are the correct return values, but
> > > > it's what the
> > > > originator of the PR requested.


> > > What if cn_nameiop is != LOOKUP but also neither DELETE nor
> > > CREATE,
> > > assuming that case is possible?  I'd leave the original if-clause
> > > at
> > > the end to catch that.

> > > ---
> > > Gary Jennejohn

> > how about this patch?

> > 1. i've added "if (cnp->cn_nameiop != LOOKUP)" although i don't
> >    think it's
> > necessary since the first blocks should cover all the possible
> > cases.
> > 2. i've used rename() to test the case (cnp->cn_nameiop != RENAME).
> >    is this
> > correct or does rename() use a combo of DELETE and CREATE? problem
> > is that the
> > rename(2) manual doesn't seem to cover the case that arg 1 is a
> > mountpoint.
> > right now EBUSY gets returned if cnp->cn_nameiop != RENAME. however
> > BUSY needs
> > to be added to all manuals which use cnp->cn_nameiop != RENAME
> > (shouldn't be
> > too many). or are there any other suggestions what rename() should
> > return if
> > arg 1 is a mountpoint?


> Hmm. In rename(2) there's

> [EINVAL]           The from argument is a parent directory of to, or
> an
>                    attempt is made to rename `.' or `..'.

> and a few lines below your patch this case is handled for ISDOTDOT
> for both RENAME and DELETE.  I don't see off hand where renaming or
> deleting "." is handled.

> According to the comment above your patch the case of "/." or "." is
> being checked, which would seem to correspond to the above part of
> rename(2), i.e. perhaps EINVAL should be returned for RENAME and
> DELETE.

> ---
> Gary Jennejohn

here's a completely new patch. all the changes are in kern/vfs_syscall.c. so
kern/vfs_lookup.c now stays just the way it is (please revert any changes from
the previous patches i posted).

after applying the patch this is the output from a slightly modified version
of the test app i attached in my very first post:

rmdir errno: 16 (EBUSY) <- EBUSY is required by POSIX
mkdir errno: 17 (EEXIST)
rename errno: 22 (EINVAL)

these are the results when called with "/" as arg. the output doesn't differ
if run with or without superuser privileges.

when run with "." as arg this is the output as regular user:

rmdir errno: 22 (EINVAL)
mkdir errno: 17 (EEXIST)
rename errno: 13 (EACCES)

and as superuser:

rmdir errno: 22 (EINVAL)
mkdir errno: 17 (EEXIST)
rename errno: 22 (EINVAL)

does this look reasonable? would be nice if mkdir and rmdir would also check
privileges at first like rename, but that's a different story i guess. ;)

alex
-------------- next part --------------
--- vfs_syscalls.c	2009-11-06 22:07:08.000000000 +0100
+++ /usr/src/sys/kern/vfs_syscalls.c	2009-11-06 21:37:47.000000000 +0100
@@ -35,7 +35,7 @@
  */
 
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
+__FBSDID("$FreeBSD: head/sys/kern/vfs_syscalls.c 196887 2009-09-06 11:44:46Z kib $");
 
 #include "opt_compat.h"
 #include "opt_kdtrace.h"
@@ -3587,8 +3587,12 @@
 	    AUDITVNODE1, pathseg, old, oldfd, td);
 #endif
 
-	if ((error = namei(&fromnd)) != 0)
+	if ((error = namei(&fromnd)) != 0) {
+		/* Translate error code for rename("/", "dir2"). */
+		if (error == EISDIR)
+			error = EINVAL;
 		return (error);
+	}
 	fvfslocked = NDHASGIANT(&fromnd);
 	tvfslocked = 0;
 #ifdef MAC
@@ -3737,8 +3741,12 @@
 	NDINIT_AT(&nd, CREATE, LOCKPARENT | SAVENAME | MPSAFE | AUDITVNODE1,
 	    segflg, path, fd, td);
 	nd.ni_cnd.cn_flags |= WILLBEDIR;
-	if ((error = namei(&nd)) != 0)
+	if ((error = namei(&nd)) != 0) {
+		/* Translate error code for mkdir("/"). */
+		if (error == EISDIR)
+			error = EEXIST;
 		return (error);
+	}
 	vfslocked = NDHASGIANT(&nd);
 	vp = nd.ni_vp;
 	if (vp != NULL) {
@@ -3825,10 +3833,15 @@
 	bwillwrite();
 	NDINIT_AT(&nd, DELETE, LOCKPARENT | LOCKLEAF | MPSAFE | AUDITVNODE1,
 	    pathseg, path, fd, td);
-	if ((error = namei(&nd)) != 0)
+	if ((error = namei(&nd)) != 0) {
+		/* Translate error code for rmdir("/"). */
+		if (error == EISDIR)
+			error = EBUSY;
 		return (error);
+	}
 	vfslocked = NDHASGIANT(&nd);
 	vp = nd.ni_vp;
+	/* XXX namei() takes care of this case. */
 	if (vp->v_type != VDIR) {
 		error = ENOTDIR;
 		goto out;
@@ -3841,6 +3854,7 @@
 		goto out;
 	}
 	/*
+	 * XXX namei() takes care of this case.
 	 * The root of a mounted filesystem cannot be deleted.
 	 */
 	if (vp->v_vflag & VV_ROOT) {