linux-kernel - Re: [PATCH v2] mm: slub: avoid deref of free pointer in sanity checks if object is invalid

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Message-ID: <aIbuks-8-FOckIjo@casper.infradead.org>
Date: Mon, 28 Jul 2025 04:29:22 +0100
From: Matthew Wilcox <willy@...radead.org>
To: liqiong <liqiong@...china.com>
Cc: Harry Yoo <harry.yoo@...cle.com>, Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] mm: slub: avoid deref of free pointer in sanity
 checks if object is invalid

On Mon, Jul 28, 2025 at 10:06:42AM +0800, liqiong wrote:
> >> In this case it's an object pointer, not a freelist pointer.
> >> Or am I misunderstanding something?
> > Actually, in alloc_debug_processing() the pointer came from slab->freelist,
> > so I think saying either "invalid freelist pointer" or
> > "invalid object pointer" make sense...
> 
> free_consistency_checks()  has 
>  'slab_err(s, slab, "Invalid object pointer 0x%p", object);'
> Maybe  it is better, alloc_consisency_checks() has the same  message.

No.  Think about it.