1 files changed, 23 insertions, 6 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index b67dbccdaf88..b3d73ad52b22 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/namei.h>
+#include <linux/seq_file.h>
 
 #include "kernfs-internal.h"
 
@@ -40,6 +41,19 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
 	return 0;
 }
 
+static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
+{
+	struct kernfs_node *node = dentry->d_fsdata;
+	struct kernfs_root *root = kernfs_root(node);
+	struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+	if (scops && scops->show_path)
+		return scops->show_path(sf, node, root);
+
+	seq_dentry(sf, dentry, " \t\n\\");
+	return 0;
+}
+
 const struct super_operations kernfs_sops = {
 	.statfs		= simple_statfs,
 	.drop_inode	= generic_delete_inode,
@@ -47,6 +61,7 @@ const struct super_operations kernfs_sops = {
 
 	.remount_fs	= kernfs_sop_remount_fs,
 	.show_options	= kernfs_sop_show_options,
+	.show_path	= kernfs_sop_show_path,
 };
 
 /**
@@ -120,9 +135,8 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 		kntmp = find_next_ancestor(kn, knparent);
 		if (WARN_ON(!kntmp))
 			return ERR_PTR(-EINVAL);
-		mutex_lock(&d_inode(dentry)->i_mutex);
-		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
-		mutex_unlock(&d_inode(dentry)->i_mutex);
+		dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
+					       strlen(kntmp->name));
 		dput(dentry);
 		if (IS_ERR(dtmp))
 			return dtmp;
@@ -138,8 +152,10 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
 	struct dentry *root;
 
 	info->sb = sb;
-	sb->s_blocksize = PAGE_CACHE_SIZE;
-	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	/* Userspace would break if executables or devices appear on sysfs */
+	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
+	sb->s_blocksize = PAGE_SIZE;
+	sb->s_blocksize_bits = PAGE_SHIFT;
 	sb->s_magic = magic;
 	sb->s_op = &kernfs_sops;
 	sb->s_time_gran = 1;
@@ -227,7 +243,8 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 	info->root = root;
 	info->ns = ns;
 
-	sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
+	sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
+			 &init_user_ns, info);
 	if (IS_ERR(sb) || sb->s_fs_info != info)
 		kfree(info);
 	if (IS_ERR(sb))