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Subject: Re: [PATCH] scripts/gdb: fix list_for_each
To:     George Prekas <prekageo@amazon.com>, linux-kernel@vger.kernel.org
Cc:     Kieran Bingham <kbingham@kernel.org>
References: <3b382958-9f1d-a3d2-a239-09ba084227e6@amazon.com>
From:   Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <2516a051-306f-670b-1f9e-d46fc577c7f8@siemens.com>
Date:   Tue, 22 Sep 2020 16:32:02 +0200
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On 22.09.20 16:28, George Prekas wrote:
> If the next pointer is NULL, list_for_each gets stuck in an infinite
> loop.
> 
> Signed-off-by: George Prekas <prekageo@amazon.com>
> ---
>   scripts/gdb/linux/lists.py | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/scripts/gdb/linux/lists.py b/scripts/gdb/linux/lists.py
> index c487ddf09d38..424a91c1aa8b 100644
> --- a/scripts/gdb/linux/lists.py
> +++ b/scripts/gdb/linux/lists.py
> @@ -27,6 +27,8 @@ def list_for_each(head):
>           raise TypeError("Must be struct list_head not {}"
>                              .format(head.type))
> 
> +    if head['next'] == 0:
> +        return
>       node = head['next'].dereference()
>       while node.address != head.address:
>           yield node.address

Obviously, infinite loops are bad and should be avoided. But NULL is 
bug, isn't it? Shouldn't we report such a corruption?

Jan

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