ANDROID: vfs: Add permission2 for filesystems with per mount permissions

This allows filesystems to use their mount private data to
influence the permssions they return in permission2. It has
been separated into a new call to avoid disrupting current
permission users.

Bug: 35848445
Bug: 120446149
Change-Id: I9d416e3b8b6eca84ef3e336bd2af89ddd51df6ca
Signed-off-by: Daniel Rosenberg <[email protected]>
[AmitP: Minor refactoring of original patch to align with
        changes from the following upstream commit
        4bfd054 ("fs: fold __inode_permission() into inode_permission()").
        Also introduce vfs_mkobj2(), because do_create()
        moved from using vfs_create() to vfs_mkobj()
        eecec19 ("mqueue: switch to vfs_mkobj(), quit abusing ->d_fsdata")
        do_create() is dropped/cleaned-up upstream so a
        minor refactoring there as well.
        066cc81 ("do_mq_open(): move all work prior to dentry_open() into a helper")]
Signed-off-by: Amit Pundir <[email protected]>
[astrachan: Folded the following changes into this patch:
            f46c9d62dd81 ("ANDROID: fs: Export vfs_rmdir2")
            9992eb8b9a1e ("ANDROID: xattr: Pass EOPNOTSUPP to permission2")]
Signed-off-by: Alistair Strachan <[email protected]>

fs/attr.c

@@ -247,7 +247,7 @@ int notify_change2(struct vfsmount *mnt, struct dentry * dentry, struct iattr *
 			return -EPERM;
 
 		if (!inode_owner_or_capable(inode)) {
-			error = inode_permission(inode, MAY_WRITE);
+			error = inode_permission2(mnt, inode, MAY_WRITE);
 			if (error)
 				return error;
 		}

fs/exec.c

@@ -1308,7 +1308,7 @@ EXPORT_SYMBOL(flush_old_exec);
 void would_dump(struct linux_binprm *bprm, struct file *file)
 {
 	struct inode *inode = file_inode(file);
-	if (inode_permission(inode, MAY_READ) < 0) {
+	if (inode_permission2(file->f_path.mnt, inode, MAY_READ) < 0) {
 		struct user_namespace *old, *user_ns;
 		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;