uprobes: change uprobe_register() to use uprobe_unregister() instead of __uprobe_unre...

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240801132739.GA8809@redhat.com

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index b33f1397dae027211c5aab8f351756805476306d..eacf287ecd89e89933a386dce41ede53a9708fac 100644 (file)
--- 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);