ipc/msg.c: fix percpu_counter use after free

These percpu counters are referenced in free_ipcs->freeque, so destroy
them later.

Fixes: 72d1e611082e ("ipc/msg: mitigate the lock contention with percpu counter")
Reported-by: syzbot+96e659d35b9d6b541152@syzkaller.appspotmail.com
Tested-by: Mark Rutland <mark.rutland@arm.com>
Cc: Jiebin Sun <jiebin.sun@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index e4e0990..fd08b3c 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -1329,11 +1329,11 @@ fail_msg_bytes:
 #ifdef CONFIG_IPC_NS
 void msg_exit_ns(struct ipc_namespace *ns)
 {
-       percpu_counter_destroy(&ns->percpu_msg_bytes);
-       percpu_counter_destroy(&ns->percpu_msg_hdrs);
        free_ipcs(ns, &msg_ids(ns), freeque);
        idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
        rhashtable_destroy(&ns->ids[IPC_MSG_IDS].key_ht);
+       percpu_counter_destroy(&ns->percpu_msg_bytes);
+       percpu_counter_destroy(&ns->percpu_msg_hdrs);
 }
 #endif