netdev - RE: [PATCH net] net: deal with integer overflows in kmalloc

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]

Date: Mon, 4 Sep 2023 08:41:01 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Eric Dumazet' <edumazet@...gle.com>, "David S . Miller"
	<davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>, syzbot
	<syzkaller@...glegroups.com>, Kyle Zeng <zengyhkyle@...il.com>, Kees Cook
	<keescook@...omium.org>, Vlastimil Babka <vbabka@...e.cz>
Subject: RE: [PATCH net] net: deal with integer overflows in kmalloc_reserve()

From: Eric Dumazet
> Sent: 31 August 2023 19:38
> 
> Blamed commit changed:
>     ptr = kmalloc(size);
>     if (ptr)
>       size = ksize(ptr);
> 
> to:
>     size = kmalloc_size_roundup(size);
>     ptr = kmalloc(size);
> 
> This allowed various crash as reported by syzbot [1]
> and Kyle Zeng.
> 
> Problem is that if @size is bigger than 0x80000001,
> kmalloc_size_roundup(size) returns 2^32.
> 
> kmalloc_reserve() uses a 32bit variable (obj_size),
> so 2^32 is truncated to 0.

Can this happen on 32bit arch?
In that case kmalloc_size_roundup() will return 0.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)