Date: Fri, 06 Nov 2009 18:42:27 +0100 (CET) From: Alexander Best <alexbestms@math.uni-muenster.de> To: <gary.jennejohn@freenet.de>, Alexander Best <alexbestms@math.uni-muenster.de> Cc: freebsd-hackers@FreeBSD.org, Alex Dupre <ale@FreeBSD.org> Subject: Re: rmdir(2) and mkdir(2) both return EISDIR for argument "/" Message-ID: <permail-200911061742271e86ffa800003d54-a_best01@message-id.uni-muenster.de> In-Reply-To: <20091106182308.14dffc50@ernst.jennejohn.org>
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Gary Jennejohn schrieb am 2009-11-06: > On Fri, 06 Nov 2009 17:43:06 +0100 (CET) > Alexander Best <alexbestms@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@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 that would be an option. however in the case of rmdir(2) EINVAL and EBUYS would both fit. depends whether be forbid deletion of / because it is a mountpoint or because / is actually /. and paths ending with . are forbidden as arg in rmdir(2). i guess we have to take a look at the POSIX specs before we can decide how to handle this. also i've discovered that permission checks for / seem to be handled differently than any other dir. on my machine /usr is a mountpoint. doing rmdir /usr returns EACCES as regular user and EBUSY as superuser. doing rmdir / as regular user however doesn't seem to check permission but returns EBUSY right away. but that's not a problem i guess. this is probably happening because the kern/vfs_lookup.c code is being executed before anything else (including permission checks). i'll have a look what POSIX has to say about the return values. but i agree with you. returning EINVAL seems logical. alex.
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