linux-kernel - Re: [PATCH 07/13] kexec: Implementation of new syscall kexec_file

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: <539F7488.9040900@zytor.com>
Date:	Mon, 16 Jun 2014 15:49:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Borislav Petkov <bp@...en8.de>, WANG Chao <chaowang@...hat.com>,
	Dave Young <dyoung@...hat.com>, mjg59@...f.ucam.org,
	bhe@...hat.com, jkosina@...e.cz, greg@...ah.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 07/13] kexec: Implementation of new syscall kexec_file_load

On 06/16/2014 02:43 PM, Vivek Goyal wrote:
>>
>> Borislav and I talked about this briefly over IRC.  A key part of that
>> is that if userspace could manipulate this system call to consume an
>> unreasonable amount of memory, we would have a problem, for example if
>> this code used vzalloc() instead of kzalloc().  However, since
>> kmalloc/kzalloc implies a relatively restrictive limit on the memory
>> allocation size anyway, well short of anything that could cause OOM
>> problems, that pretty much solves the problem.
> 
> Actually currently I am using vzalloc() for command line buffer
> allocation.
> 
> 	image->cmdline_buf = vzalloc(cmdline_len);
> 	if (!image->cmdline_buf)
> 		goto out;
> 
> Should I switch to using kzalloc() instead?
> 

Yes.  There is absolutely no valid reason to use vzalloc() for an object
that small, and if someone manipulates the header to allow for a crazily
large command line then you can trick the kernel into allocating
arbitrary amounts of memory.

	-hpa


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/