From: Harry Yoo <harry@kernel.org>
To: Karl Mehltretter <kmehltretter@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Hao Li <hao.li@linux.dev>, Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shengming Hu <hu.shengming@zte.com.cn>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/slub: initialize the free pointer of the bootstrap kmem_cache_node
Date: Thu, 15 Oct 2026 17:18:52 +0100 [thread overview]
Message-ID: <atD8CeImfP79s-9b@thinkstation> (raw)
In-Reply-To: <20261010203906.93156-1-kmehltretter@gmail.com>
On Sat, Oct 10, 2026 at 10:39:06PM +0200, Karl Mehltretter wrote:
> With slub_debug=FZPU, validating kmem_cache_node reports
>
> BUG kmem_cache_node (Not tainted): Freepointer corrupt
> Object 0xffff888000140040 @offset=64 fp=0x5a5a5a5a5a5a5a5a
>
> and taints the kernel. Poisoning places the bootstrap object's free
> pointer outside the object, where check_object() checks it even while
> allocated.
>
> early_kmem_cache_node_alloc() previously took this object from a
> freelist with an initialized pointer. It now takes it from the slab
> iterator and builds the freelist only for the remaining objects,
> leaving its pointer filled with POISON_INUSE.
>
> Initialize the bootstrap object's free pointer to NULL.
>
> Fixes: dc795d4c0282 ("mm/slub: defer freelist construction until after bulk allocation from a new slab")
> Assisted-by: LLM
> Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
> ---
Looks good to me,
Reviewed-by: Harry Yoo (Meta) <harry@kernel.org>
--
Cheers,
Harry / Hyeonggon
next prev parent reply other threads:[~2026-10-15 16:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-10 20:39 [PATCH] mm/slub: initialize the free pointer of the bootstrap kmem_cache_node Karl Mehltretter
2026-10-15 16:18 ` Harry Yoo [this message]
2026-10-15 16:31 ` Harry Yoo (Meta)
2026-10-15 16:47 ` Vlastimil Babka (SUSE)
2026-10-16 1:24 ` hu.shengming
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