From: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Lance Yang <lance.yang@linux.dev>,
akpm@linux-foundation.org, david@redhat.com,
lorenzo.stoakes@oracle.com
Cc: ziy@nvidia.com, Liam.Howlett@oracle.com, npache@redhat.com,
ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org,
ioworker0@gmail.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH mm-new 1/1] mm/khugepaged: guard is_zero_pfn() calls with pte_present()
Date: Fri, 17 Oct 2025 16:10:06 +0800 [thread overview]
Message-ID: <cdd47a33-d0c5-4e7d-a210-fb3236e6749c@linux.alibaba.com> (raw)
In-Reply-To: <20251016033643.10848-1-lance.yang@linux.dev>
On 2025/10/16 11:36, Lance Yang wrote:
> From: Lance Yang <lance.yang@linux.dev>
>
> A non-present entry, like a swap PTE, contains completely different data
> (swap type and offset). pte_pfn() doesn't know this, so if we feed it a
> non-present entry, it will spit out a junk PFN.
>
> What if that junk PFN happens to match the zeropage's PFN by sheer
> chance? While really unlikely, this would be really bad if it did.
>
> So, let's fix this potential bug by ensuring all calls to is_zero_pfn()
> in khugepaged.c are properly guarded by a pte_present() check.
>
> Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Signed-off-by: Lance Yang <lance.yang@linux.dev>
> ---
LGTM.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
prev parent reply other threads:[~2025-10-17 8:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-16 3:36 Lance Yang
2025-10-16 5:34 ` Dev Jain
2025-10-16 5:59 ` Lance Yang
2025-10-16 6:15 ` Dev Jain
2025-10-16 6:17 ` Dev Jain
2025-10-16 6:26 ` Lance Yang
2025-10-17 1:27 ` Wei Yang
2025-10-17 8:11 ` David Hildenbrand
2025-10-17 8:37 ` Lance Yang
2025-10-17 8:43 ` David Hildenbrand
2025-10-17 8:47 ` Lance Yang
2025-10-17 9:35 ` Lorenzo Stoakes
2025-10-16 9:33 ` Wei Yang
2025-10-16 10:51 ` Lance Yang
2025-10-17 8:10 ` Baolin Wang [this message]
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