[PATCH 3.17 54/73] userns: Allow setting gid_maps without privilege when setgroups is disabled

From: Greg Kroah-Hartman
Date: Tue Jan 06 2015 - 21:28:57 EST


3.17-stable review patch. If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

commit 66d2f338ee4c449396b6f99f5e75cd18eb6df272 upstream.

Now that setgroups can be disabled and not reenabled, setting gid_map
without privielge can now be enabled when setgroups is disabled.

This restores most of the functionality that was lost when unprivileged
setting of gid_map was removed. Applications that use this functionality
will need to check to see if they use setgroups or init_groups, and if they
don't they can be fixed by simply disabling setgroups before writing to
gid_map.

Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/user_namespace.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -826,6 +826,11 @@ static bool new_idmap_permitted(const st
kuid_t uid = make_kuid(ns->parent, id);
if (uid_eq(uid, cred->euid))
return true;
+ } else if (cap_setid == CAP_SETGID) {
+ kgid_t gid = make_kgid(ns->parent, id);
+ if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
+ gid_eq(gid, cred->egid))
+ return true;
}
}



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