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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <61528e45-b2a7-5ef9-09dd-9cdc63c4599e@omp.ru>
Date: Mon, 12 Aug 2024 12:41:03 +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()

Hello!

   Failed to notice an issue with the subject in the internal review;
I think it should look like "net: ppp: bsd_comp: fix integer overflow
in bsd_decompress()"...

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

> After that, the higher 32 bits in accm will be set to 1.

   Only if we have 1 in the bit 31 after shl %cl,%eax...

> Cast the result of the expression to unsigned long.

   I strongly suspect we should re-declare accm as *unsigned int*
instead...

> Found by Linux Verification Center (linuxtesting.org) with Svace.
> 
> Signed-off-by: Roman Smirnov <r.smirnov@....ru>
> ---
>  drivers/net/ppp/bsd_comp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ppp/bsd_comp.c b/drivers/net/ppp/bsd_comp.c
> index 55954594e157..078fe8c9bee8 100644
> --- a/drivers/net/ppp/bsd_comp.c
> +++ b/drivers/net/ppp/bsd_comp.c
> @@ -918,7 +918,7 @@ static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
>  	 */
>  
>  	bitno -= 8;
> -	accm  |= *ibuf++ << bitno;
> +	accm  |= (unsigned long)(*ibuf++) << bitno;
>  	if (tgtbitno < bitno)
>  	  {
>  	    continue;
> 

MBR, Sergey