From: Harry Yoo <harry.yoo@oracle.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/6] slab: don't validate slab pointer in free_debug_processing()
Date: Fri, 12 Sep 2025 19:52:56 +0900 [thread overview]
Message-ID: <aMP7iOwAm-nC4ZYH@hyeyoo> (raw)
In-Reply-To: <20250911-slub-slab-validation-v1-6-8b67eb3b3dc5@suse.cz>
On Thu, Sep 11, 2025 at 07:02:39PM +0200, Vlastimil Babka wrote:
> The struct slab pointer has been obtained one from the object being
> freed on all the paths that lead to this function. In all cases this
> already includes the test for slab type of the struct page which struct
> slab is overlaying. Thus we would not reach this function if it was
> not a valid slab pointer in the first place.
>
> One less obvious case is that kmem_cache_free() trusts virt_to_slab()
> blindly so it may be NULL if the slab type check is false. But with
> SLAB_CONSISTENCY_CHECKS, cache_from_obj() called also from
> kmem_cache_free() catches this and returns NULL, which terminates
> freeing immediately.
Oh, I thought it'll crash even with debug caches
but it won't and I misread the code.
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
--
Cheers,
Harry / Hyeonggon
prev parent reply other threads:[~2025-09-12 10:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-11 17:02 [PATCH 0/6] slab: struct slab pointer validation improvements Vlastimil Babka
2025-09-11 17:02 ` [PATCH 1/6] slab: Remove dead code in free_consistency_checks() Vlastimil Babka
2025-09-11 17:02 ` [PATCH 2/6] slab: wrap debug slab validation in validate_slab_ptr() Vlastimil Babka
2025-09-12 10:20 ` Harry Yoo
2025-09-11 17:02 ` [PATCH 3/6] slab: move validate_slab_ptr() from check_slab() to its callers Vlastimil Babka
2025-09-12 10:24 ` Harry Yoo
2025-09-11 17:02 ` [PATCH 4/6] slab: move validate_slab_ptr() from alloc_consistency_checks() to its caller Vlastimil Babka
2025-09-12 10:41 ` Harry Yoo
2025-09-11 17:02 ` [PATCH 5/6] slab: validate slab before using it in alloc_single_from_partial() Vlastimil Babka
2025-09-12 10:48 ` Harry Yoo
2025-09-12 11:34 ` Vlastimil Babka
2025-09-11 17:02 ` [PATCH 6/6] slab: don't validate slab pointer in free_debug_processing() Vlastimil Babka
2025-09-12 10:52 ` Harry Yoo [this message]
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