linux-kernel - Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap

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: <20250317055304.GB26662@lst.de>
Date: Mon, 17 Mar 2025 06:53:04 +0100
From: Christoph Hellwig <hch@....de>
To: Bingbu Cao <bingbu.cao@...ux.intel.com>
Cc: Huan Yang <link@...o.com>, hch@....de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	lorenzo.stoakes@...cle.com, opensource.kernel@...o.com,
	rppt@...nel.org, ryan.roberts@....com, urezki@...il.com,
	ziy@...dia.com
Subject: Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap_pfns

On Mon, Mar 17, 2025 at 01:29:05PM +0800, Bingbu Cao wrote:
> Why not update udmabuf to make it work with both vmap_pfns() and
> vmap()? As only the udmabuf knows it is actually working on?
> 
> I don't think it's a good idea to hack the common API, the WARN_ON()
> is really a mandatory check, and current case is a good example.

What non-page backed memory does udmabuf try to work on, and more
importantly how does it actually work on them given that the normal
DMA APIs require page backed memory.  Or is this just made it up
and it doesn't work at all given that it also tries to dma map
to the fake miscdevice struct device which can't work for most
cases?

Mapping non-page memory is difficult and without having coherent theory
of what non-page memory you are mapping and being very careful you
are extremely unlikely to get it right.