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-rw-r--r--kernel/user.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/user.c b/kernel/user.c
index 6408c042429..220e586127a 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -187,6 +187,17 @@ void switch_uid(struct user_struct *new_user)
atomic_dec(&old_user->processes);
switch_uid_keyring(new_user);
current->user = new_user;
+
+ /*
+ * We need to synchronize with __sigqueue_alloc()
+ * doing a get_uid(p->user).. If that saw the old
+ * user value, we need to wait until it has exited
+ * its critical region before we can free the old
+ * structure.
+ */
+ smp_mb();
+ spin_unlock_wait(&current->sighand->siglock);
+
free_uid(old_user);
suid_keys(current);
}