From: "J. Bruce Fields" <bfields@fieldses.org>
To: Oleg Drokin <green@linuxhacker.ru>
Cc: Jeff Layton <jlayton@poochiereds.net>,
linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] nfsd: Make creates return EEXIST correctly instead of EPERM
Date: Fri, 8 Jul 2016 16:54:13 -0400 [thread overview]
Message-ID: <20160708205413.GC11269@fieldses.org> (raw)
In-Reply-To: <1467942466-3081422-1-git-send-email-green@linuxhacker.ru>
On Thu, Jul 07, 2016 at 09:47:46PM -0400, Oleg Drokin wrote:
> It looks like we are bit overzealous about failing mkdir/create/mknod
> with permission denied if the parent dir is not writeable.
> Need to make sure the name does not exist first, because we need to
> return EEXIST in that case.
>
> Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
> ---
> A very similar problem exists with symlinks, but the patch is more
> involved, so assuming this one is ok, I'll send a symlink one separately.
> fs/nfsd/nfs4proc.c | 6 +++++-
> fs/nfsd/vfs.c | 11 ++++++++++-
> 2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index de1ff1d..0067520 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -605,8 +605,12 @@ nfsd4_create(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>
> fh_init(&resfh, NFS4_FHSIZE);
>
> + /*
> + * We just check thta parent is accessible here, nfsd_* do their
> + * own access permission checks
> + */
> status = fh_verify(rqstp, &cstate->current_fh, S_IFDIR,
> - NFSD_MAY_CREATE);
> + NFSD_MAY_EXEC);
> if (status)
> return status;
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 6fbd81e..6a45ec6 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1161,7 +1161,11 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
> if (isdotent(fname, flen))
> goto out;
>
> - err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
> + /*
> + * Even though it is a create, first we see if we are even allowed
> + * to peek inside the parent
> + */
> + err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
Looks like in the v3 case we haven't actually locked the directory yet
at this point so this check is a little race-prone.
I wonder why the code's structured that way--it's confusing.
--b.
> if (err)
> goto out;
>
> @@ -1211,6 +1215,11 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
> goto out;
> }
>
> + /* Now let's see if we actually have permissions to create */
> + err = nfsd_permission(rqstp, fhp->fh_export, dentry, NFSD_MAY_CREATE);
> + if (err)
> + goto out;
> +
> if (!(iap->ia_valid & ATTR_MODE))
> iap->ia_mode = 0;
> iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
> --
> 2.7.4
next prev parent reply other threads:[~2016-07-08 20:54 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-08 1:47 [PATCH] nfsd: Make creates return EEXIST correctly instead of EPERM Oleg Drokin
2016-07-08 11:02 ` Jeff Layton
2016-07-08 15:14 ` Oleg Drokin
2016-07-08 15:53 ` Jeff Layton
2016-07-08 15:59 ` Oleg Drokin
2016-07-08 16:17 ` Jeff Layton
2016-07-08 16:28 ` Oleg Drokin
2016-07-09 2:52 ` Al Viro
2016-07-09 2:58 ` Oleg Drokin
2016-07-09 3:13 ` Al Viro
2016-07-08 16:04 ` J. Bruce Fields
2016-07-08 16:16 ` Oleg Drokin
2016-07-08 20:49 ` J. Bruce Fields
2016-07-08 21:47 ` Oleg Drokin
2016-07-09 3:10 ` Al Viro
2016-07-09 3:41 ` Oleg Drokin
2016-07-13 19:00 ` J. Bruce Fields
2016-07-08 20:54 ` J. Bruce Fields [this message]
2016-07-08 21:53 ` Oleg Drokin
2016-07-21 20:34 ` J. Bruce Fields
2016-07-21 20:37 ` Oleg Drokin
2016-07-22 1:57 ` J. Bruce Fields
2016-07-22 6:35 ` Oleg Drokin
2016-07-22 10:55 ` J. Bruce Fields
2016-07-22 15:13 ` Oleg Drokin
2016-07-22 17:48 ` J. Bruce Fields
2016-07-22 17:48 ` [PATCH 1/7] nfsd: Make creates return EEXIST instead of EACCES J. Bruce Fields
2016-07-22 17:48 ` [PATCH 2/7] nfsd: remove redundant zero-length check from create J. Bruce Fields
2016-07-22 17:48 ` [PATCH 3/7] nfsd: remove redundant i_lookup check J. Bruce Fields
2016-07-24 0:22 ` Al Viro
2016-07-24 12:10 ` J. Bruce Fields
2016-07-24 14:23 ` Al Viro
2016-07-24 20:21 ` J. Bruce Fields
2016-07-22 17:48 ` [PATCH 4/7] nfsd: reorganize nfsd_create J. Bruce Fields
2016-07-22 17:48 ` [PATCH 5/7] nfsd: remove unnecessary positive-dentry check J. Bruce Fields
2016-07-22 17:48 ` [PATCH 6/7] nfsd: clean up bad-type check in nfsd_create_locked J. Bruce Fields
2016-07-22 17:48 ` [PATCH 7/7] nfsd: drop unnecessary MAY_EXEC check from create J. Bruce Fields
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