[CFT][PATCH 8/8] userns: Allow setting gid_maps without privilege when setgroups is disabled

From: Eric W. Biederman
Date: Tue Dec 09 2014 - 15:45:40 EST

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

Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
kernel/user_namespace.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index b507f9af7ff2..3b29b9a52332 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -826,6 +826,11 @@ static bool new_idmap_permitted(const struct file *file,
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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