[PATCH v4 7/9] uprobes: change uprobe_register() to use uprobe_unregister() instead of __uprobe_unregister()

[Oleg Nesterov <oleg@redhat.com>]

If register_for_each_vma() fails uprobe_register() can safely drop
uprobe->register_rwsem and use uprobe_unregister(). There is no worry
about the races with another register/unregister, consumer_add() was
already called so this case doesn't differ from _unregister() right
after the successful _register().

Yes this means the extra up_write() + down_write(), but this is the
slow and unlikely case anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/events/uprobes.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 974474680820..5ea0aabe8774 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1174,16 +1174,18 @@ struct uprobe *uprobe_register(struct inode *inode,
 	if (likely(uprobe_is_active(uprobe))) {
 		consumer_add(uprobe, uc);
 		ret = register_for_each_vma(uprobe, uc);
-		if (ret)
-			__uprobe_unregister(uprobe, uc);
 	}
 	up_write(&uprobe->register_rwsem);
 	put_uprobe(uprobe);
 
-	if (unlikely(ret == -EAGAIN))
-		goto retry;
+	if (ret) {
+		if (unlikely(ret == -EAGAIN))
+			goto retry;
+		uprobe_unregister(uprobe, uc);
+		return ERR_PTR(ret);
+	}
 
-	return ret ? ERR_PTR(ret) : uprobe;
+	return uprobe;
 }
 EXPORT_SYMBOL_GPL(uprobe_register);
 
-- 
2.25.1.362.g51ebf55