AFS fixes

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Merge tag 'afs-fixes-20171201' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull AFS fixes from David Howells:
 "Two fix patches for the AFS filesystem:

   - Fix the refcounting on permit caching.

   - AFS inode (afs_vnode) fields need resetting after allocation
     because they're only initialised when slab pages are obtained from
     the page allocator"

* tag 'afs-fixes-20171201' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Properly reset afs_vnode (inode) fields
  afs: Fix permit refcounting

fs/afs/internal.h

@@ -441,7 +441,10 @@ enum afs_lock_state {
 };
 
 /*
- * AFS inode private data
+ * AFS inode private data.
+ *
+ * Note that afs_alloc_inode() *must* reset anything that could incorrectly
+ * leak from one inode to another.
  */
 struct afs_vnode {
 	struct inode		vfs_inode;	/* the VFS's inode record */

fs/afs/security.c

@@ -120,7 +120,7 @@ static void afs_hash_permits(struct afs_permits *permits)
 void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
 		      unsigned int cb_break)
 {
-	struct afs_permits *permits, *xpermits, *replacement, *new = NULL;
+	struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
 	afs_access_t caller_access = READ_ONCE(vnode->status.caller_access);
 	size_t size = 0;
 	bool changed = false;
@@ -204,7 +204,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
 	new = kzalloc(sizeof(struct afs_permits) +
 		      sizeof(struct afs_permit) * size, GFP_NOFS);
 	if (!new)
-		return;
+		goto out_put;
 
 	refcount_set(&new->usage, 1);
 	new->nr_permits = size;
@@ -229,8 +229,6 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
 
 	afs_hash_permits(new);
 
-	afs_put_permits(permits);
-
 	/* Now see if the permit list we want is actually already available */
 	spin_lock(&afs_permits_lock);
 
@@ -262,11 +260,15 @@ found:
 	kfree(new);
 
 	spin_lock(&vnode->lock);
-	if (cb_break != (vnode->cb_break + vnode->cb_interest->server->cb_s_break) ||
-	    permits != rcu_access_pointer(vnode->permit_cache))
-		goto someone_else_changed_it_unlock;
+	zap = rcu_access_pointer(vnode->permit_cache);
+	if (cb_break == (vnode->cb_break + vnode->cb_interest->server->cb_s_break) &&
+	    zap == permits)
 		rcu_assign_pointer(vnode->permit_cache, replacement);
+	else
+		zap = replacement;
 	spin_unlock(&vnode->lock);
+	afs_put_permits(zap);
+out_put:
 	afs_put_permits(permits);
 	return;
 

fs/afs/super.c

@@ -536,7 +536,9 @@ static void afs_kill_super(struct super_block *sb)
 }
 
 /*
- * initialise an inode cache slab element prior to any use
+ * Initialise an inode cache slab element prior to any use.  Note that
+ * afs_alloc_inode() *must* reset anything that could incorrectly leak from one
+ * inode to another.
  */
 static void afs_i_init_once(void *_vnode)
 {
@@ -568,11 +570,21 @@ static struct inode *afs_alloc_inode(struct super_block *sb)
 
 	atomic_inc(&afs_count_active_inodes);
 
+	/* Reset anything that shouldn't leak from one inode to the next. */
 	memset(&vnode->fid, 0, sizeof(vnode->fid));
 	memset(&vnode->status, 0, sizeof(vnode->status));
 
 	vnode->volume		= NULL;
+	vnode->lock_key		= NULL;
+	vnode->permit_cache	= NULL;
+	vnode->cb_interest	= NULL;
+#ifdef CONFIG_AFS_FSCACHE
+	vnode->cache		= NULL;
+#endif
+
 	vnode->flags		= 1 << AFS_VNODE_UNSET;
+	vnode->cb_type		= 0;
+	vnode->lock_state	= AFS_VNODE_LOCK_NONE;
 
 	_leave(" = %p", &vnode->vfs_inode);
 	return &vnode->vfs_inode;