netdev - Re: [PATCH] drivers: net: bsd_comp: fix integer overflow in bsd

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Message-ID: <bd95f568-a4cd-6ffa-9260-fa261f40f252@omp.ru>
Date: Mon, 12 Aug 2024 12:54:40 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Roman Smirnov <r.smirnov@....ru>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Breno Leitao <leitao@...ian.org>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Karina Yankevich
	<k.yankevich@....ru>, <lvc-project@...uxtesting.org>
Subject: Re: [PATCH] drivers: net: bsd_comp: fix integer overflow in
 bsd_decompress()

On 8/12/24 12:41 PM, Sergey Shtylyov wrote:

[...]

> On 8/12/24 11:43 AM, Roman Smirnov wrote:
> 
>> The result of a bit shift has type int.
> 
>    So far, so good... :-)
> 
>> If ibuf is greater than or
> 
>    *ibuf maybe? :-)
> 
>> equal to 128, a sign switch will occur.
> 
>    I wonder whether you had looked at the .lsy file before writing
> that...
>    Actually, movzvl (%rdi),%eax is used when reading *buf, so no 

   It was movzbl, of course...

> sign extension occurs at this point... it occurs when casting the 
> result of shift to *unsignjed long*

   ... before ORing with accm.

[...]

MBR, Sergey