linux-kernel - Re: [PATCH v3] arm64: Restrict pagetable teardown to avoid false warning

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Message-ID: <aEhfY2D-njOEBFst@arm.com>
Date: Tue, 10 Jun 2025 17:37:55 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Dev Jain <dev.jain@....com>
Cc: will@...nel.org, david@...hat.com, ryan.roberts@....com,
	anshuman.khandual@....com, mark.rutland@....com,
	yang@...amperecomputing.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH v3] arm64: Restrict pagetable teardown to avoid false
 warning

On Tue, May 27, 2025 at 01:56:33PM +0530, Dev Jain wrote:
> Commit 9c006972c3fe removes the pxd_present() checks because the caller
> checks pxd_present(). But, in case of vmap_try_huge_pud(), the caller only
> checks pud_present(); pud_free_pmd_page() recurses on each pmd through
> pmd_free_pte_page(), wherein the pmd may be none. Thus it is possible to
> hit a warning in the latter, since pmd_none => !pmd_table(). Thus, add
> a pmd_present() check in pud_free_pmd_page().
> 
> This problem was found by code inspection.
> 
> Fixes: 9c006972c3fe (arm64: mmu: drop pXd_present() checks from pXd_free_pYd_table())
> Cc: <stable@...r.kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>