linux-kernel - Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if called with __GFP

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: Wed, 8 May 2024 21:51:15 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Hailong Liu <hailong.liu@...o.com>
Cc: Gao Xiang <hsiangkao@...ux.alibaba.com>, akpm@...ux-foundation.org,
	Michal Hocko <mhocko@...e.com>, urezki@...il.com, hch@...radead.org,
	lstoakes@...il.com, 21cnbao@...il.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, xiang@...nel.org, chao@...nel.org,
	Oven <liyangouwen1@...o.com>
Subject: Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if
 called with __GFP_NOFAIL

On Thu, May 09, 2024 at 09:30:59AM +0800, Hailong Liu wrote:
> I’m not suggesting that erofs would cause a memleak. What I mean is
> that if kvmalloc is invoked with __GFP_NOFAIL, it must ensure a non-NULL
> return, even in scenarios where memory leaks caused by other processes
> result in the inability to allocate a page. In such a situation, it
> should result in “Kernel panic - not syncing: System is deadlocked
> on memory”.

Yes.  __GFP_NOFAIL is a contract that says never ever return NULL.
The callers will generally not handle a NULL return and blindly
dereference it, leading to all kinds of nasty security issues.

Note that deadlocking would be nice, but at least it is just a
denial of service and not a possible privilege escalation.