ovl: check whiteout on lowest layer as well

Not checking whiteouts on lowest layer was an optimization (there's nothing
to white out there), but it could result in inconsitent behavior when a
layer previously used as upper/middle is later used as lowest. 

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

2 files changed, 50 insertions, 56 deletions

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index dfef6ca53dfe..9df848f2e622 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -80,23 +80,50 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
         return NULL;
 }
 
-static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
+static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir,
+                                                   const char *name, int len,
                                                    u64 ino, unsigned int d_type)
 {
         struct ovl_cache_entry *p;
         size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);
 
         p = kmalloc(size, GFP_KERNEL);
-        if (p) {
-                memcpy(p->name, name, len);
-                p->name[len] = '\0';
-                p->len = len;
-                p->type = d_type;
-                p->ino = ino;
-                p->is_whiteout = false;
-                p->is_cursor = false;
-        }
+        if (!p)
+                return NULL;
+
+        memcpy(p->name, name, len);
+        p->name[len] = '\0';
+        p->len = len;
+        p->type = d_type;
+        p->ino = ino;
+        p->is_whiteout = false;
+        p->is_cursor = false;
+
+        if (d_type == DT_CHR) {
+                struct dentry *dentry;
+                const struct cred *old_cred;
+                struct cred *override_cred;
+
+                override_cred = prepare_creds();
+                if (!override_cred) {
+                        kfree(p);
+                        return NULL;
+                }
 
+                /*
+                 * CAP_DAC_OVERRIDE for lookup
+                 */
+                cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+                old_cred = override_creds(override_cred);
+
+                dentry = lookup_one_len(name, dir, len);
+                if (!IS_ERR(dentry)) {
+                        p->is_whiteout = ovl_is_whiteout(dentry);
+                        dput(dentry);
+                }
+                revert_creds(old_cred);
+                put_cred(override_cred);
+        }
         return p;
 }
 
@@ -123,36 +150,10 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
                         return 0;
         }
 
-        p = ovl_cache_entry_new(name, len, ino, d_type);
+        p = ovl_cache_entry_new(rdd->dir, name, len, ino, d_type);
         if (p == NULL)
                 return -ENOMEM;
 
-        if (d_type == DT_CHR) {
-                struct dentry *dentry;
-                const struct cred *old_cred;
-                struct cred *override_cred;
-
-                override_cred = prepare_creds();
-                if (!override_cred) {
-                        kfree(p);
-                        return -ENOMEM;
-                }
-
-                /*
-                 * CAP_DAC_OVERRIDE for lookup
-                 */
-                cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
-                old_cred = override_creds(override_cred);
-
-                dentry = lookup_one_len(name, rdd->dir, len);
-                if (!IS_ERR(dentry)) {
-                        p->is_whiteout = ovl_is_whiteout(dentry);
-                        dput(dentry);
-                }
-                revert_creds(old_cred);
-                put_cred(override_cred);
-        }
-
         list_add_tail(&p->l_node, rdd->list);
         rb_link_node(&p->node, parent, newp);
         rb_insert_color(&p->node, &rdd->root);
@@ -170,7 +171,7 @@ static int ovl_fill_lower(struct ovl_readdir_data *rdd,
         if (p) {
                 list_move_tail(&p->l_node, &rdd->middle);
         } else {
-                p = ovl_cache_entry_new(name, namelen, ino, d_type);
+                p = ovl_cache_entry_new(rdd->dir, name, namelen, ino, d_type);
                 if (p == NULL)
                         rdd->err = -ENOMEM;
                 else
@@ -229,6 +230,7 @@ static inline int ovl_dir_read(struct path *realpath,
         if (IS_ERR(realfile))
                 return PTR_ERR(realfile);
 
+        rdd->dir = realpath->dentry;
         rdd->ctx.pos = 0;
         do {
                 rdd->count = 0;
@@ -274,7 +276,6 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
                 next = ovl_path_next(idx, dentry, &realpath);
 
                 if (next != -1) {
-                        rdd.dir = realpath.dentry;
                         err = ovl_dir_read(&realpath, &rdd);
                         if (err)
                                 break;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f72b82fdc1e6..5dbc6789fd5f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -350,16 +350,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 if (IS_ERR(this))
                         goto out;
 
-                /*
-                 * If this is not the lowermost layer, check whiteout and opaque
-                 * directory.
-                 */
-                if (poe->numlower && this) {
+                if (this) {
                         if (ovl_is_whiteout(this)) {
                                 dput(this);
                                 this = NULL;
                                 upperopaque = true;
-                        } else if (ovl_is_opaquedir(this)) {
+                        } else if (poe->numlower && ovl_is_opaquedir(this)) {
                                 upperopaque = true;
                         }
                 }
@@ -384,19 +380,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                         goto out_put;
                 if (!this)
                         continue;
-
+                if (ovl_is_whiteout(this)) {
+                        dput(this);
+                        break;
+                }
                 /*
-                 * If this is not the lowermost layer, check whiteout and opaque
-                 * directory.
+                 * Only makes sense to check opaque dir if this is not the
+                 * lowermost layer.
                  */
-                if (i < poe->numlower - 1) {
-                        if (ovl_is_whiteout(this)) {
-                                dput(this);
-                                break;
-                        } else if (ovl_is_opaquedir(this)) {
-                                opaque = true;
-                        }
-                }
+                if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
+                        opaque = true;
                 /*
                  * If this is a non-directory then stop here.
                  *