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
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/inode.c b/fs/inode.c
index 16fefd3..a21d5a9 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -25,6 +25,7 @@
#include <linux/async.h>
#include <linux/posix_acl.h>
#include <linux/ima.h>
+#include <linux/cred.h>
/*
* This is needed for the following functions:
@@ -1733,3 +1734,19 @@
inode->i_mode = mode;
}
EXPORT_SYMBOL(inode_init_owner);
+
+/*
+ * return true if current either has CAP_FOWNER to the
+ * file, or owns the file.
+ */
+bool is_owner_or_cap(const struct inode *inode)
+{
+ struct user_namespace *ns = inode_userns(inode);
+
+ if (current_user_ns() == ns && current_fsuid() == inode->i_uid)
+ return true;
+ if (ns_capable(ns, CAP_FOWNER))
+ return true;
+ return false;
+}
+EXPORT_SYMBOL(is_owner_or_cap);