netdev - Re: [PATCH] mm: Decline to manipulate the refcount on a slab page

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: <Z9Ka8-aGagGH0rd5@infradead.org>
Date: Thu, 13 Mar 2025 01:44:35 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Hannes Reinecke <hare@...e.de>
Cc: Christoph Hellwig <hch@...radead.org>,
	Matthew Wilcox <willy@...radead.org>,
	Jakub Kicinski <kuba@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, netdev@...r.kernel.org,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org
Subject: Re: [PATCH] mm: Decline to manipulate the refcount on a slab page

On Thu, Mar 13, 2025 at 09:34:39AM +0100, Hannes Reinecke wrote:
> nvmf_connect_command_prep() returns a kmalloced buffer.

Yes.

> That is stored in a bvec in _nvme_submit_sync_cmd() via
> blk_mq_rq_map_kern()->bio_map_kern().
> And from that point on we are dealing with bvecs (iterators
> and all), and losing the information that the page referenced
> is a slab page.

Yes. But so does every other consomer of the block layer that passes
slab memory, of which there are quite a few.  Various internal scsi
and nvme command come to mind, as does the XFS buffer cache.

> The argument is that the network layer expected a kvec iterator
> when slab pages are referred to, not a bvec iterator.

It doesn't.  It just doesn't want you to use ->sendpage.