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nfsd: fix EXDEV checking in rename

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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>
This commit is contained in:
J. Bruce Fields 2013-04-15 16:03:46 -04:00
parent 030d794bf4
commit aa387d6ce1
1 changed files with 2 additions and 4 deletions
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6
fs/nfsd/vfs.c
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@ -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)