linux-kernel - Re: [PATCH V2] x86/mm: Fix NULL pointer dereference in kernel_page

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Message-ID: <CAPdGtUz15wt_MqYaRy_0_krr11Dgjkhg7H_kXjFwyKoHAk8JZA@mail.gmail.com>
Date: Fri, 24 Jan 2025 22:17:49 +0530
From: Tanya Agarwal <tanyaagarwal25699@...il.com>
To: dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org, 
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc: x86@...nel.org, hpa@...or.com, kirill.shutemov@...ux.intel.com, 
	rick.p.edgecombe@...el.com, akpm@...ux-foundation.org, 
	skhan@...uxfoundation.org, anupnewsmail@...il.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] x86/mm: Fix NULL pointer dereference in kernel_page_present()

On Sat, Jan 11, 2025 at 11:28 PM Tanya Agarwal
<tanyaagarwal25699@...il.com> wrote:
>
> From: Tanya Agarwal <tanyaagarwal25699@...il.com>
>
> The static code analysis tool "Coverity Scan" pointed the following
> details out for further development considerations:
> CID 1271215: Dereference null return value (NULL_RETURNS)
> dereference: Dereferencing pte, which is known to be NULL.
>
> Conclusion:
> Add WARN_ON_ONCE() and NULL check for pte before dereferencing it.
>
> Fixes: 8a235efad548 ("Hibernation: Handle DEBUG_PAGEALLOC on x86")
> Signed-off-by: Tanya Agarwal <tanyaagarwal25699@...il.com>
> ---
> V2: add WARN_ON_ONCE() as suggested by Dave
>
> Coverity Link:
> https://scan5.scan.coverity.com/#/project-view/63683/10063?selectedIssue=1271215
>
>  arch/x86/mm/pat/set_memory.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 95bc50a8541c..8f9d418e6a8c 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -2495,6 +2495,9 @@ bool kernel_page_present(struct page *page)
>                 return false;
>
>         pte = lookup_address((unsigned long)page_address(page), &level);
> +       if (WARN_ON_ONCE(!pte))
> +               return false;
> +
>         return (pte_val(*pte) & _PAGE_PRESENT);
>  }
>
> --
> 2.39.5
>

Hi Dave,

I just wanted to check if you've had a chance to review it or need any
more information.

Thanks,
Tanya