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>

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index dfef6ca..9df848f 100644 (file)
--- 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 f72b82f..5dbc678 100644 (file)
--- 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.
                 *