ovl: check mounter creds on underlying lookup
authorMiklos Szeredi <mszeredi@redhat.com>
Fri, 29 Jul 2016 10:05:22 +0000 (12:05 +0200)
committerMiklos Szeredi <mszeredi@redhat.com>
Fri, 29 Jul 2016 10:05:22 +0000 (12:05 +0200)
The hash salting changes meant that we can no longer reuse the hash in the
overlay dentry to look up the underlying dentry.

Instead of lookup_hash(), use lookup_one_len_unlocked() and swith to
mounter's creds (like we do for all other operations later in the series).

Now the lookup_hash() export introduced in 4.6 by 3c9fe8cdff1b ("vfs: add
lookup_hash() helper") is unused and can possibly be removed; its
usefulness negated by the hash salting and the idea that mounter's creds
should be used on operations on underlying filesystems.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 8387ff2577eb ("vfs: make the string hashes salt the hash")

fs/overlayfs/super.c

index 5e254b3a8c5601256d8960ed66a304081210cce1..cbfa0398f9dabf22ae47697da33e7f0328d29c6c 100644 (file)
@@ -423,12 +423,16 @@ static bool ovl_dentry_weird(struct dentry *dentry)
                                  DCACHE_OP_COMPARE);
 }
 
-static inline struct dentry *ovl_lookup_real(struct dentry *dir,
+static inline struct dentry *ovl_lookup_real(struct super_block *ovl_sb,
+                                            struct dentry *dir,
                                             struct qstr *name)
 {
+       const struct cred *old_cred;
        struct dentry *dentry;
 
-       dentry = lookup_hash(name, dir);
+       old_cred = ovl_override_creds(ovl_sb);
+       dentry = lookup_one_len_unlocked(name->name, dir, name->len);
+       revert_creds(old_cred);
 
        if (IS_ERR(dentry)) {
                if (PTR_ERR(dentry) == -ENOENT)
@@ -481,7 +485,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 
        upperdir = ovl_upperdentry_dereference(poe);
        if (upperdir) {
-               this = ovl_lookup_real(upperdir, &dentry->d_name);
+               this = ovl_lookup_real(dentry->d_sb, upperdir, &dentry->d_name);
                err = PTR_ERR(this);
                if (IS_ERR(this))
                        goto out;
@@ -514,7 +518,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                bool opaque = false;
                struct path lowerpath = poe->lowerstack[i];
 
-               this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
+               this = ovl_lookup_real(dentry->d_sb,
+                                      lowerpath.dentry, &dentry->d_name);
                err = PTR_ERR(this);
                if (IS_ERR(this)) {
                        /*