Merge tag 'landlock_v34' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull Landlock LSM from James Morris:
 "Add Landlock, a new LSM from Mickaël Salaün.

  Briefly, Landlock provides for unprivileged application sandboxing.

  From Mickaël's cover letter:
    "The goal of Landlock is to enable to restrict ambient rights (e.g.
     global filesystem access) for a set of processes. Because Landlock
     is a stackable LSM [1], it makes possible to create safe security
     sandboxes as new security layers in addition to the existing
     system-wide access-controls. This kind of sandbox is expected to
     help mitigate the security impact of bugs or unexpected/malicious
     behaviors in user-space applications. Landlock empowers any
     process, including unprivileged ones, to securely restrict
     themselves.

     Landlock is inspired by seccomp-bpf but instead of filtering
     syscalls and their raw arguments, a Landlock rule can restrict the
     use of kernel objects like file hierarchies, according to the
     kernel semantic. Landlock also takes inspiration from other OS
     sandbox mechanisms: XNU Sandbox, FreeBSD Capsicum or OpenBSD
     Pledge/Unveil.

     In this current form, Landlock misses some access-control features.
     This enables to minimize this patch series and ease review. This
     series still addresses multiple use cases, especially with the
     combined use of seccomp-bpf: applications with built-in sandboxing,
     init systems, security sandbox tools and security-oriented APIs [2]"

  The cover letter and v34 posting is here:

      https://lore.kernel.org/linux-security-module/20210422154123.13086-1-mic@digikod.net/

  See also:

      https://landlock.io/

  This code has had extensive design discussion and review over several
  years"

Link: https://lore.kernel.org/lkml/50db058a-7dde-441b-a7f9-f6837fe8b69f@schaufler-ca.com/ [1]
Link: https://lore.kernel.org/lkml/f646e1c7-33cf-333f-070c-0a40ad0468cd@digikod.net/ [2]

* tag 'landlock_v34' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  landlock: Enable user space to infer supported features
  landlock: Add user and kernel documentation
  samples/landlock: Add a sandbox manager example
  selftests/landlock: Add user space tests
  landlock: Add syscall implementations
  arch: Wire up Landlock syscalls
  fs,security: Add sb_delete hook
  landlock: Support filesystem access-control
  LSM: Infrastructure management of the superblock
  landlock: Add ptrace restrictions
  landlock: Set up the security framework and manage credentials
  landlock: Add ruleset and domain management
  landlock: Add object management

security/security.c

@@ -203,6 +203,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_inode, &blob_sizes.lbs_inode);
 	lsm_set_blob_size(&needed->lbs_ipc, &blob_sizes.lbs_ipc);
 	lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
+	lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
 	lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
 }
 
@@ -333,12 +334,13 @@ static void __init ordered_lsm_init(void)
 	for (lsm = ordered_lsms; *lsm; lsm++)
 		prepare_lsm(*lsm);
 
-	init_debug("cred blob size     = %d\n", blob_sizes.lbs_cred);
-	init_debug("file blob size     = %d\n", blob_sizes.lbs_file);
-	init_debug("inode blob size    = %d\n", blob_sizes.lbs_inode);
-	init_debug("ipc blob size      = %d\n", blob_sizes.lbs_ipc);
-	init_debug("msg_msg blob size  = %d\n", blob_sizes.lbs_msg_msg);
-	init_debug("task blob size     = %d\n", blob_sizes.lbs_task);
+	init_debug("cred blob size       = %d\n", blob_sizes.lbs_cred);
+	init_debug("file blob size       = %d\n", blob_sizes.lbs_file);
+	init_debug("inode blob size      = %d\n", blob_sizes.lbs_inode);
+	init_debug("ipc blob size        = %d\n", blob_sizes.lbs_ipc);
+	init_debug("msg_msg blob size    = %d\n", blob_sizes.lbs_msg_msg);
+	init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
+	init_debug("task blob size       = %d\n", blob_sizes.lbs_task);
 
 	/*
 	 * Create any kmem_caches needed for blobs
@@ -670,6 +672,27 @@ static void __init lsm_early_task(struct task_struct *task)
 		panic("%s: Early task alloc failed.\n", __func__);
 }
 
+/**
+ * lsm_superblock_alloc - allocate a composite superblock blob
+ * @sb: the superblock that needs a blob
+ *
+ * Allocate the superblock blob for all the modules
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+static int lsm_superblock_alloc(struct super_block *sb)
+{
+	if (blob_sizes.lbs_superblock == 0) {
+		sb->s_security = NULL;
+		return 0;
+	}
+
+	sb->s_security = kzalloc(blob_sizes.lbs_superblock, GFP_KERNEL);
+	if (sb->s_security == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
 /*
  * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
  * can be accessed with:
@@ -867,12 +890,26 @@ int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *
 
 int security_sb_alloc(struct super_block *sb)
 {
-	return call_int_hook(sb_alloc_security, 0, sb);
+	int rc = lsm_superblock_alloc(sb);
+
+	if (unlikely(rc))
+		return rc;
+	rc = call_int_hook(sb_alloc_security, 0, sb);
+	if (unlikely(rc))
+		security_sb_free(sb);
+	return rc;
+}
+
+void security_sb_delete(struct super_block *sb)
+{
+	call_void_hook(sb_delete, sb);
 }
 
 void security_sb_free(struct super_block *sb)
 {
 	call_void_hook(sb_free_security, sb);
+	kfree(sb->s_security);
+	sb->s_security = NULL;
 }
 
 void security_free_mnt_opts(void **mnt_opts)