netdev - Re: [PATCH net] net: Fix undefined behavior in netdev name allocation

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Message-ID: <20231113230902.7f342501@kernel.org>
Date: Mon, 13 Nov 2023 23:09:02 -0500
From: Jakub Kicinski <kuba@...nel.org>
To: Gal Pressman <gal@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>, Vlad
 Buslov <vladbu@...dia.com>
Subject: Re: [PATCH net] net: Fix undefined behavior in netdev name
 allocation

On Mon, 13 Nov 2023 10:35:44 +0200 Gal Pressman wrote:
> Cited commit removed the strscpy() call and kept the snprintf() only.
> 
> When allocating a netdev, 'res' and 'name' pointers are equal, but
> according to POSIX, if copying takes place between objects that overlap
> as a result of a call to sprintf() or snprintf(), the results are
> undefined.
> 
> Add back the strscpy() and use 'buf' as an intermediate buffer.

It may be worth mentioning that it is fairly common to put the format
in dev->name before device is registered, IOW this condition takes
place a lot? IIUC once we cross into 3-digit IDs we may crash?

With that and the right fixes tag:

Reviewed-by: Jakub Kicinski <kuba@...nel.org>

Thanks!
-- 
pw-bot: cr