gfs2_drevalidate(): use stable parent inode and name passed by caller

No need to mess with dget_parent() for the former; for the latter we really should
not rely upon ->d_name.name remaining stable.  Theoretically a UAF, but it's
hard to exfiltrate the information...

Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
index 86c338901fab56745aeaa22f05f0febb78ed8940..95050e719233db5dea3ff4394816efdf70a15767 100644 (file)
--- a/fs/gfs2/dentry.c
+++ b/fs/gfs2/dentry.c
@@ -35,48 +35,40 @@
 static int gfs2_drevalidate(struct inode *dir, const struct qstr *name,
                            struct dentry *dentry, unsigned int flags)
 {
-       struct dentry *parent;
-       struct gfs2_sbd *sdp;
-       struct gfs2_inode *dip;
+       struct gfs2_sbd *sdp = GFS2_SB(dir);
+       struct gfs2_inode *dip = GFS2_I(dir);
        struct inode *inode;
        struct gfs2_holder d_gh;
        struct gfs2_inode *ip = NULL;
-       int error, valid = 0;
+       int error, valid;
        int had_lock = 0;
 
        if (flags & LOOKUP_RCU)
                return -ECHILD;
 
-       parent = dget_parent(dentry);
-       sdp = GFS2_SB(d_inode(parent));
-       dip = GFS2_I(d_inode(parent));
        inode = d_inode(dentry);
 
        if (inode) {
                if (is_bad_inode(inode))
-                       goto out;
+                       return 0;
                ip = GFS2_I(inode);
        }
 
-       if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL) {
-               valid = 1;
-               goto out;
-       }
+       if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL)
+               return 1;
 
        had_lock = (gfs2_glock_is_locked_by_me(dip->i_gl) != NULL);
        if (!had_lock) {
                error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
                if (error)
-                       goto out;
+                       return 0;
        }
 
-       error = gfs2_dir_check(d_inode(parent), &dentry->d_name, ip);
+       error = gfs2_dir_check(dir, name, ip);
        valid = inode ? !error : (error == -ENOENT);
 
        if (!had_lock)
                gfs2_glock_dq_uninit(&d_gh);
-out:
-       dput(parent);
        return valid;
 }