Commit aa387d6c authored Apr 15, 2013 by J. Bruce Fields

nfsd: fix EXDEV checking in rename



We again check for the EXDEV a little later on, so the first check is
redundant.  This check is also slightly racier, since a badly timed
eviction from the export cache could leave us with the two fh_export
pointers pointing to two different cache entries which each refer to the
same underlying export.

It's better to compare vfsmounts as the later check does, but that
leaves a minor security hole in the case where the two exports refer to
two different directories especially if (for example) they have
different root-squashing options.

So, compare ex_path.dentry too.

Reported-by: Joe Habermann <joe.habermann@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent 030d794b

fs/nfsd/vfs.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -1758,10 +1758,6 @@ nfsd_rename(struct svc_rqst rqstp, struct svc_fh ffhp, char *fname, int flen,
		tdentry = tfhp->fh_dentry;
		tdir = tdentry->d_inode;

		err = (rqstp->rq_vers == 2) ? nfserr_acces : nfserr_xdev;
		if (ffhp->fh_export != tfhp->fh_export)
		goto out;

		err = nfserr_perm;
		if (!flen \|\| isdotent(fname, flen) \|\| !tlen \|\| isdotent(tname, tlen))
		goto out;
		@@ -1802,6 +1798,8 @@ nfsd_rename(struct svc_rqst rqstp, struct svc_fh ffhp, char *fname, int flen,
		host_err = -EXDEV;
		if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
		goto out_dput_new;
		if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
		goto out_dput_new;

		host_err = nfsd_break_lease(odentry->d_inode);
		if (host_err)

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