From: Harry Yoo <harry@kernel.org>
To: Zi Yan <ziy@nvidia.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>,
Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/slab: reject unsupported kmalloc() sizes
Date: Wed, 2 Sep 2026 12:12:50 +0100 [thread overview]
Message-ID: <apgEYg6IdJlBmUwE@nixos> (raw)
In-Reply-To: <20260830-limit_kmalloc_size-v2-1-bf4ca9c63c88@nvidia.com>
On Sun, Aug 30, 2026 at 10:23:23PM -0400, Zi Yan wrote:
> kmalloc() is used to allocate physically contiguous memory for kernel
> allocations. For requests larger than KMALLOC_MAX_CACHE_SIZE, kmalloc()
> uses the page allocator and can only support up to KMALLOC_MAX_SIZE. For
> request sizes bigger than KMALLOC_MAX_SIZE, the page allocator can emit a
> WARN because kmalloc() allocates an order greater than MAX_PAGE_ORDER. To
> make the KMALLOC_MAX_SIZE limit more explicit instead of relying on the
> page allocator check, add a KMALLOC_MAX_SIZE check inside kmalloc() to emit
> a WARN and return NULL for requested sizes bigger than KMALLOC_MAX_SIZE.
> Like the WARN in the page allocator and kvmalloc(), allow __GFP_NOWARN to
> suppress the WARN.
>
> Suggested-by: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
Looks good to me,
Reviewed-by: Harry Yoo (Meta) <harry@kernel.org>
--
Cheers,
Harry / Hyeonggon
prev parent reply other threads:[~2026-09-02 11:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 2:23 [PATCH v2] mm/slab: reject unsupported kmalloc() sizes Zi Yan
2026-08-31 9:46 ` Vlastimil Babka (SUSE)
2026-09-02 11:12 ` Harry Yoo [this message]
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