userns: userns: check user namespace for task->file uid equivalence checks

Cheat for now and say all files belong to init_user_ns.  Next step will be
to let superblocks belong to a user_ns, and derive inode_userns(inode)
from inode->i_sb->s_user_ns.  Finally we'll introduce more flexible
arrangements.

Changelog:
	Feb 15: make is_owner_or_cap take const struct inode
	Feb 23: make is_owner_or_cap bool

[[email protected]: coding-style fixes]
Signed-off-by: Serge E. Hallyn <[email protected]>
Acked-by: "Eric W. Biederman" <[email protected]>
Acked-by: Daniel Lezcano <[email protected]>
Acked-by: David Howells <[email protected]>
Cc: James Morris <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 12529e966350..9eebc646d14a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1457,8 +1457,13 @@ enum {
 #define put_fs_excl() atomic_dec(&current->fs_excl)
 #define has_fs_excl() atomic_read(&current->fs_excl)
 
-#define is_owner_or_cap(inode)	\
-	((current_fsuid() == (inode)->i_uid) || capable(CAP_FOWNER))
+/*
+ * until VFS tracks user namespaces for inodes, just make all files
+ * belong to init_user_ns
+ */
+extern struct user_namespace init_user_ns;
+#define inode_userns(inode) (&init_user_ns)
+extern bool is_owner_or_cap(const struct inode *inode);
 
 /* not quite ready to be deprecated, but... */
 extern void lock_super(struct super_block *);