Merge 5.15.52 into android14-5.15

Changes in 5.15.52
	tick/nohz: unexport __init-annotated tick_nohz_full_setup()
	x86, kvm: use proper ASM macros for kvm_vcpu_is_preempted
	bcache: memset on stack variables in bch_btree_check() and bch_sectors_dirty_init()
	xfs: use kmem_cache_free() for kmem_cache objects
	xfs: punch out data fork delalloc blocks on COW writeback failure
	xfs: Fix the free logic of state in xfs_attr_node_hasname
	xfs: remove all COW fork extents when remounting readonly
	xfs: check sb_meta_uuid for dabuf buffer recovery
	xfs: prevent UAF in xfs_log_item_in_current_chkpt
	xfs: only bother with sync_filesystem during readonly remount
	powerpc/ftrace: Remove ftrace init tramp once kernel init is complete
	fs: add is_idmapped_mnt() helper
	fs: move mapping helpers
	fs: tweak fsuidgid_has_mapping()
	fs: account for filesystem mappings
	docs: update mapping documentation
	fs: use low-level mapping helpers
	fs: remove unused low-level mapping helpers
	fs: port higher-level mapping helpers
	fs: add i_user_ns() helper
	fs: support mapped mounts of mapped filesystems
	fs: fix acl translation
	fs: account for group membership
	rtw88: 8821c: support RFE type4 wifi NIC
	rtw88: rtw8821c: enable rfe 6 devices
	net: mscc: ocelot: allow unregistered IP multicast flooding to CPU
	io_uring: fix not locked access to fixed buf table
	Linux 5.15.52

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Icfb690703efd8cab1dffa7ca6cce28bbca635c3d

fs/namespace.c

@@ -31,6 +31,7 @@
 #include <uapi/linux/mount.h>
 #include <linux/fs_context.h>
 #include <linux/shmem_fs.h>
+#include <linux/mnt_idmapping.h>
 
 #include "pnode.h"
 #include "internal.h"
@@ -561,7 +562,7 @@ static void free_vfsmnt(struct mount *mnt)
 	struct user_namespace *mnt_userns;
 
 	mnt_userns = mnt_user_ns(&mnt->mnt);
-	if (mnt_userns != &init_user_ns)
+	if (!initial_idmapping(mnt_userns))
 		put_user_ns(mnt_userns);
 	kfree_const(mnt->mnt_devname);
 #ifdef CONFIG_SMP
@@ -965,6 +966,7 @@ static struct mount *skip_mnt_tree(struct mount *p)
 struct vfsmount *vfs_create_mount(struct fs_context *fc)
 {
 	struct mount *mnt;
+	struct user_namespace *fs_userns;
 
 	if (!fc->root)
 		return ERR_PTR(-EINVAL);
@@ -982,6 +984,10 @@ struct vfsmount *vfs_create_mount(struct fs_context *fc)
 	mnt->mnt_mountpoint	= mnt->mnt.mnt_root;
 	mnt->mnt_parent		= mnt;
 
+	fs_userns = mnt->mnt.mnt_sb->s_user_ns;
+	if (!initial_idmapping(fs_userns))
+		mnt->mnt.mnt_userns = get_user_ns(fs_userns);
+
 	lock_mount_hash();
 	list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
 	unlock_mount_hash();
@@ -1072,7 +1078,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 
 	atomic_inc(&sb->s_active);
 	mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt);
-	if (mnt->mnt.mnt_userns != &init_user_ns)
+	if (!initial_idmapping(mnt->mnt.mnt_userns))
 		mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns);
 	mnt->mnt.mnt_sb = sb;
 	mnt->mnt.mnt_root = dget(root);
@@ -3927,28 +3933,32 @@ static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
 static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
 {
 	struct vfsmount *m = &mnt->mnt;
+	struct user_namespace *fs_userns = m->mnt_sb->s_user_ns;
 
 	if (!kattr->mnt_userns)
 		return 0;
 
+	/*
+	 * Creating an idmapped mount with the filesystem wide idmapping
+	 * doesn't make sense so block that. We don't allow mushy semantics.
+	 */
+	if (kattr->mnt_userns == fs_userns)
+		return -EINVAL;
+
 	/*
 	 * Once a mount has been idmapped we don't allow it to change its
 	 * mapping. It makes things simpler and callers can just create
 	 * another bind-mount they can idmap if they want to.
 	 */
-	if (mnt_user_ns(m) != &init_user_ns)
+	if (is_idmapped_mnt(m))
 		return -EPERM;
 
 	/* The underlying filesystem doesn't support idmapped mounts yet. */
 	if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
 		return -EINVAL;
 
-	/* Don't yet support filesystem mountable in user namespaces. */
-	if (m->mnt_sb->s_user_ns != &init_user_ns)
-		return -EINVAL;
-
 	/* We're not controlling the superblock. */
-	if (!capable(CAP_SYS_ADMIN))
+	if (!ns_capable(fs_userns, CAP_SYS_ADMIN))
 		return -EPERM;
 
 	/* Mount has already been visible in the filesystem hierarchy. */
@@ -4002,14 +4012,27 @@ out:
 
 static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
 {
-	struct user_namespace *mnt_userns;
+	struct user_namespace *mnt_userns, *old_mnt_userns;
 
 	if (!kattr->mnt_userns)
 		return;
 
+	/*
+	 * We're the only ones able to change the mount's idmapping. So
+	 * mnt->mnt.mnt_userns is stable and we can retrieve it directly.
+	 */
+	old_mnt_userns = mnt->mnt.mnt_userns;
+
 	mnt_userns = get_user_ns(kattr->mnt_userns);
 	/* Pairs with smp_load_acquire() in mnt_user_ns(). */
 	smp_store_release(&mnt->mnt.mnt_userns, mnt_userns);
+
+	/*
+	 * If this is an idmapped filesystem drop the reference we've taken
+	 * in vfs_create_mount() before.
+	 */
+	if (!initial_idmapping(old_mnt_userns))
+		put_user_ns(old_mnt_userns);
 }
 
 static void mount_setattr_commit(struct mount_kattr *kattr,
@@ -4133,13 +4156,15 @@ static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
 	}
 
 	/*
-	 * The init_user_ns is used to indicate that a vfsmount is not idmapped.
-	 * This is simpler than just having to treat NULL as unmapped. Users
-	 * wanting to idmap a mount to init_user_ns can just use a namespace
-	 * with an identity mapping.
+	 * The initial idmapping cannot be used to create an idmapped
+	 * mount. We use the initial idmapping as an indicator of a mount
+	 * that is not idmapped. It can simply be passed into helpers that
+	 * are aware of idmapped mounts as a convenient shortcut. A user
+	 * can just create a dedicated identity mapping to achieve the same
+	 * result.
 	 */
 	mnt_userns = container_of(ns, struct user_namespace, ns);
-	if (mnt_userns == &init_user_ns) {
+	if (initial_idmapping(mnt_userns)) {
 		err = -EPERM;
 		goto out_fput;
 	}