uprobes: Change filter_chain() to iterate ->consumers list

Now that it safe to use ->consumer_rwsem under ->mmap_sem we can
almost finish the implementation of filter_chain(). It still lacks
the actual uc->filter(...) call but othewrwise it is ready, just
it pretends that ->filter() always returns true.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 61d0fa6b5012..4d0452363686 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -614,14 +614,19 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
 
 static bool filter_chain(struct uprobe *uprobe)
 {
-        /*
-         * TODO:
-         *      for_each_consumer(uc)
-         *              if (uc->filter(...))
-         *                      return true;
-         *      return false;
-         */
-        return uprobe->consumers != NULL;
+        struct uprobe_consumer *uc;
+        bool ret = false;
+
+        down_read(&uprobe->consumer_rwsem);
+        for (uc = uprobe->consumers; uc; uc = uc->next) {
+                /* TODO: ret = uc->filter(...) */
+                ret = true;
+                if (ret)
+                        break;
+        }
+        up_read(&uprobe->consumer_rwsem);
+
+        return ret;
 }
 
 static int