All parameters of posix messages queues (queues_max/msg_max/msgsize_max)
end up being limited by RLIMIT_MSGQUEUE. The code in mqueue_get_inode is
where that limiting happens.
The RLIMIT_MSGQUEUE is bound to the user namespace and is counted
hierarchically.
We can allow root in the user namespace to modify the posix messages
queues parameters.
Signed-off-by: Alexey Gladkov <[email protected]>
---
ipc/mq_sysctl.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index fbf6a8b93a26..5e573c657775 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -12,6 +12,7 @@
#include <linux/stat.h>
#include <linux/capability.h>
#include <linux/slab.h>
+#include <linux/cred.h>
static int msg_max_limit_min = MIN_MSGMAX;
static int msg_max_limit_max = HARD_MSGMAX;
@@ -76,8 +77,45 @@ static int set_is_seen(struct ctl_table_set *set)
return ¤t->nsproxy->ipc_ns->mq_set == set;
}
+static void mq_set_ownership(struct ctl_table_header *head,
+ struct ctl_table *table,
+ kuid_t *uid, kgid_t *gid)
+{
+ struct ipc_namespace *ns =
+ container_of(head->set, struct ipc_namespace, mq_set);
+
+ kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+ kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+ *uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+ *gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
+static int mq_permissions(struct ctl_table_header *head, struct ctl_table *table)
+{
+ struct ipc_namespace *ns =
+ container_of(head->set, struct ipc_namespace, mq_set);
+ int mode = table->mode;
+ kuid_t ns_root_uid;
+ kgid_t ns_root_gid;
+
+ mq_set_ownership(head, table, &ns_root_uid, &ns_root_gid);
+
+ if (uid_eq(current_euid(), ns_root_uid))
+ mode >>= 6;
+
+ if (in_egroup_p(ns_root_gid))
+ mode >>= 3;
+
+ mode &= 7;
+
+ return (mode << 6) | (mode << 3) | mode;
+}
+
static struct ctl_table_root set_root = {
.lookup = set_lookup,
+ .permissions = mq_permissions,
+ .set_ownership = mq_set_ownership,
};
bool setup_mq_sysctls(struct ipc_namespace *ns)
--
2.33.4