Linux 6.9-rc1

[linux-2.6-microblaze.git] / ipc / namespace.c

diff --git a/ipc/namespace.c b/ipc/namespace.c
index e1fcaed..6ecc30e 100644 (file)
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -19,6 +19,12 @@
 
 #include "util.h"
 
+/*
+ * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
+ */
+static void free_ipc(struct work_struct *unused);
+static DECLARE_WORK(free_ipc_work, free_ipc);
+
 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
 {
        return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
@@ -37,9 +43,18 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
        int err;
 
        err = -ENOSPC;
+ again:
        ucounts = inc_ipc_namespaces(user_ns);
-       if (!ucounts)
+       if (!ucounts) {
+               /*
+                * IPC namespaces are freed asynchronously, by free_ipc_work.
+                * If frees were pending, flush_work will wait, and
+                * return true. Fail the allocation if no frees are pending.
+                */
+               if (flush_work(&free_ipc_work))
+                       goto again;
                goto fail;
+       }
 
        err = -ENOMEM;
        ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
@@ -66,8 +81,11 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
        if (!setup_ipc_sysctls(ns))
                goto fail_mq;
 
+       err = msg_init_ns(ns);
+       if (err)
+               goto fail_put;
+
        sem_init_ns(ns);
-       msg_init_ns(ns);
        shm_init_ns(ns);
 
        return ns;
@@ -127,10 +145,11 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 
 static void free_ipc_ns(struct ipc_namespace *ns)
 {
-       /* mq_put_mnt() waits for a grace period as kern_unmount()
-        * uses synchronize_rcu().
+       /*
+        * Caller needs to wait for an RCU grace period to have passed
+        * after making the mount point inaccessible to new accesses.
         */
-       mq_put_mnt(ns);
+       mntput(ns->mq_mnt);
        sem_exit_ns(ns);
        msg_exit_ns(ns);
        shm_exit_ns(ns);
@@ -150,15 +169,16 @@ static void free_ipc(struct work_struct *unused)
        struct llist_node *node = llist_del_all(&free_ipc_list);
        struct ipc_namespace *n, *t;
 
+       llist_for_each_entry_safe(n, t, node, mnt_llist)
+               mnt_make_shortterm(n->mq_mnt);
+
+       /* Wait for any last users to have gone away. */
+       synchronize_rcu();
+
        llist_for_each_entry_safe(n, t, node, mnt_llist)
                free_ipc_ns(n);
 }
 
-/*
- * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
- */
-static DECLARE_WORK(free_ipc_work, free_ipc);
-
 /*
  * put_ipc_ns - drop a reference to an ipc namespace.
  * @ns: the namespace to put