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nfsd: vfs_mkdir() might succeed leaving dentry negative unhashed 

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...

Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-05-11 17:03:19 -04:00
parent 9c3e9025a3
commit 3819bb0d79
1 changed files with 22 additions and 0 deletions
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22
fs/nfsd/vfs.c
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@ -1201,6 +1201,28 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
break;
case S_IFDIR:
host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
if (!host_err && unlikely(d_unhashed(dchild))) {
struct dentry *d;
d = lookup_one_len(dchild->d_name.name,
dchild->d_parent,
dchild->d_name.len);
if (IS_ERR(d)) {
host_err = PTR_ERR(d);
break;
}
if (unlikely(d_is_negative(d))) {
dput(d);
err = nfserr_serverfault;
goto out;
}
dput(resfhp->fh_dentry);
resfhp->fh_dentry = dget(d);
err = fh_update(resfhp);
dput(dchild);
dchild = d;
if (err)
goto out;
}
break;
case S_IFCHR:
case S_IFBLK: