Merge tag 'v4.9.120' into v4.9-rt

This is the 4.9.120 stable release

7 files changed, 110 insertions, 37 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 20eb11d5061d..f97376545156 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -353,14 +353,11 @@ static void dentry_unlink_inode(struct dentry * dentry)
 	__releases(dentry->d_inode->i_lock)
 {
 	struct inode *inode = dentry->d_inode;
-	bool hashed = !d_unhashed(dentry);
 
-	if (hashed)
-		raw_write_seqcount_begin(&dentry->d_seq);
+	raw_write_seqcount_begin(&dentry->d_seq);
 	__d_clear_type_and_inode(dentry);
 	hlist_del_init(&dentry->d_u.d_alias);
-	if (hashed)
-		raw_write_seqcount_end(&dentry->d_seq);
+	raw_write_seqcount_end(&dentry->d_seq);
 	spin_unlock(&dentry->d_lock);
 	spin_unlock(&inode->i_lock);
 	if (!inode->i_nlink)
@@ -1926,10 +1923,12 @@ struct dentry *d_make_root(struct inode *root_inode)
 
 	if (root_inode) {
 		res = __d_alloc(root_inode->i_sb, NULL);
-		if (res)
+		if (res) {
+			res->d_flags |= DCACHE_RCUACCESS;
 			d_instantiate(res, root_inode);
-		else
+		} else {
 			iput(root_inode);
+		}
 	}
 	return res;
 }
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index ffaf66a51de3..4f78e099de1d 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1316,7 +1316,10 @@ int ext4_init_inode_table(struct super_block *sb, ext4_group_t group,
 			    ext4_itable_unused_count(sb, gdp)),
 			    sbi->s_inodes_per_block);
 
-	if ((used_blks < 0) || (used_blks > sbi->s_itb_per_group)) {
+	if ((used_blks < 0) || (used_blks > sbi->s_itb_per_group) ||
+	    ((group == 0) && ((EXT4_INODES_PER_GROUP(sb) -
+			       ext4_itable_unused_count(sb, gdp)) <
+			      EXT4_FIRST_INO(sb)))) {
 		ext4_error(sb, "Something is wrong with group %u: "
 			   "used itable blocks: %d; "
 			   "itable unused count: %u",
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6cbb0f7ead2f..9d44b3683b46 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3031,14 +3031,8 @@ static ext4_group_t ext4_has_uninit_itable(struct super_block *sb)
 		if (!gdp)
 			continue;
 
-		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED))
-			continue;
-		if (group != 0)
+		if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED)))
 			break;
-		ext4_error(sb, "Inode table for bg 0 marked as "
-			   "needing zeroing");
-		if (sb->s_flags & MS_RDONLY)
-			return ngroups;
 	}
 
 	return group;
diff --git a/fs/namespace.c b/fs/namespace.c
index ffa9923ff4f7..4935d21d5d0c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -607,12 +607,21 @@ int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
 		return 0;
 	mnt = real_mount(bastard);
 	mnt_add_count(mnt, 1);
+	smp_mb();			// see mntput_no_expire()
 	if (likely(!read_seqretry(&mount_lock, seq)))
 		return 0;
 	if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
 		mnt_add_count(mnt, -1);
 		return 1;
 	}
+	lock_mount_hash();
+	if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
+		mnt_add_count(mnt, -1);
+		unlock_mount_hash();
+		return 1;
+	}
+	unlock_mount_hash();
+	/* caller will mntput() */
 	return -1;
 }
 
@@ -1143,12 +1152,27 @@ static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
 static void mntput_no_expire(struct mount *mnt)
 {
 	rcu_read_lock();
-	mnt_add_count(mnt, -1);
-	if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
+	if (likely(READ_ONCE(mnt->mnt_ns))) {
+		/*
+		 * Since we don't do lock_mount_hash() here,
+		 * ->mnt_ns can change under us.  However, if it's
+		 * non-NULL, then there's a reference that won't
+		 * be dropped until after an RCU delay done after
+		 * turning ->mnt_ns NULL.  So if we observe it
+		 * non-NULL under rcu_read_lock(), the reference
+		 * we are dropping is not the final one.
+		 */
+		mnt_add_count(mnt, -1);
 		rcu_read_unlock();
 		return;
 	}
 	lock_mount_hash();
+	/*
+	 * make sure that if __legitimize_mnt() has not seen us grab
+	 * mount_lock, we'll see their refcount increment here.
+	 */
+	smp_mb();
+	mnt_add_count(mnt, -1);
 	if (mnt_get_count(mnt)) {
 		rcu_read_unlock();
 		unlock_mount_hash();
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index e69ebe648a34..c2afe39f0b9e 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -43,10 +43,11 @@ static void proc_evict_inode(struct inode *inode)
 	de = PDE(inode);
 	if (de)
 		pde_put(de);
+
 	head = PROC_I(inode)->sysctl;
 	if (head) {
 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
-		sysctl_head_put(head);
+		proc_sys_evict_inode(inode, head);
 	}
 }
 
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 5378441ec1b7..c0bdeceaaeb6 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -65,6 +65,7 @@ struct proc_inode {
 	struct proc_dir_entry *pde;
 	struct ctl_table_header *sysctl;
 	struct ctl_table *sysctl_entry;
+	struct hlist_node sysctl_inodes;
 	const struct proc_ns_operations *ns_ops;
 	struct inode vfs_inode;
 };
@@ -249,10 +250,12 @@ extern void proc_thread_self_init(void);
  */
 #ifdef CONFIG_PROC_SYSCTL
 extern int proc_sys_init(void);
-extern void sysctl_head_put(struct ctl_table_header *);
+extern void proc_sys_evict_inode(struct inode *inode,
+				 struct ctl_table_header *head);
 #else
 static inline void proc_sys_init(void) { }
-static inline void sysctl_head_put(struct ctl_table_header *head) { }
+static inline void proc_sys_evict_inode(struct  inode *inode,
+					struct ctl_table_header *head) { }
 #endif
 
 /*
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 8e9c3f3f90a5..c8e7d1a6b474 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -190,6 +190,7 @@ static void init_header(struct ctl_table_header *head,
 	head->set = set;
 	head->parent = NULL;
 	head->node = node;
+	INIT_HLIST_HEAD(&head->inodes);
 	if (node) {
 		struct ctl_table *entry;
 		for (entry = table; entry->procname; entry++, node++)
@@ -259,6 +260,44 @@ static void unuse_table(struct ctl_table_header *p)
 			complete(p->unregistering);
 }
 
+static void proc_sys_prune_dcache(struct ctl_table_header *head)
+{
+	struct inode *inode;
+	struct proc_inode *ei;
+	struct hlist_node *node;
+	struct super_block *sb;
+
+	rcu_read_lock();
+	for (;;) {
+		node = hlist_first_rcu(&head->inodes);
+		if (!node)
+			break;
+		ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
+		spin_lock(&sysctl_lock);
+		hlist_del_init_rcu(&ei->sysctl_inodes);
+		spin_unlock(&sysctl_lock);
+
+		inode = &ei->vfs_inode;
+		sb = inode->i_sb;
+		if (!atomic_inc_not_zero(&sb->s_active))
+			continue;
+		inode = igrab(inode);
+		rcu_read_unlock();
+		if (unlikely(!inode)) {
+			deactivate_super(sb);
+			rcu_read_lock();
+			continue;
+		}
+
+		d_prune_aliases(inode);
+		iput(inode);
+		deactivate_super(sb);
+
+		rcu_read_lock();
+	}
+	rcu_read_unlock();
+}
+
 /* called under sysctl_lock, will reacquire if has to wait */
 static void start_unregistering(struct ctl_table_header *p)
 {
@@ -272,31 +311,22 @@ static void start_unregistering(struct ctl_table_header *p)
 		p->unregistering = &wait;
 		spin_unlock(&sysctl_lock);
 		wait_for_completion(&wait);
-		spin_lock(&sysctl_lock);
 	} else {
 		/* anything non-NULL; we'll never dereference it */
 		p->unregistering = ERR_PTR(-EINVAL);
+		spin_unlock(&sysctl_lock);
 	}
 	/*
+	 * Prune dentries for unregistered sysctls: namespaced sysctls
+	 * can have duplicate names and contaminate dcache very badly.
+	 */
+	proc_sys_prune_dcache(p);
+	/*
 	 * do not remove from the list until nobody holds it; walking the
 	 * list in do_sysctl() relies on that.
 	 */
-	erase_header(p);
-}
-
-static void sysctl_head_get(struct ctl_table_header *head)
-{
 	spin_lock(&sysctl_lock);
-	head->count++;
-	spin_unlock(&sysctl_lock);
-}
-
-void sysctl_head_put(struct ctl_table_header *head)
-{
-	spin_lock(&sysctl_lock);
-	if (!--head->count)
-		kfree_rcu(head, rcu);
-	spin_unlock(&sysctl_lock);
+	erase_header(p);
 }
 
 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
@@ -440,10 +470,20 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
 
 	inode->i_ino = get_next_ino();
 
-	sysctl_head_get(head);
 	ei = PROC_I(inode);
+
+	spin_lock(&sysctl_lock);
+	if (unlikely(head->unregistering)) {
+		spin_unlock(&sysctl_lock);
+		iput(inode);
+		inode = NULL;
+		goto out;
+	}
 	ei->sysctl = head;
 	ei->sysctl_entry = table;
+	hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
+	head->count++;
+	spin_unlock(&sysctl_lock);
 
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 	inode->i_mode = table->mode;
@@ -466,6 +506,15 @@ out:
 	return inode;
 }
 
+void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
+{
+	spin_lock(&sysctl_lock);
+	hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
+	if (!--head->count)
+		kfree_rcu(head, rcu);
+	spin_unlock(&sysctl_lock);
+}
+
 static struct ctl_table_header *grab_header(struct inode *inode)
 {
 	struct ctl_table_header *head = PROC_I(inode)->sysctl;