From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm64: fix erroneous warnings in page freeing functions
Date: Thu, 6 Sep 2018 14:52:25 +0100 [thread overview]
Message-ID: <20180906135225.GB5212@arm.com> (raw)
In-Reply-To: <20180905163857.7933-1-mark.rutland@arm.com>
On Wed, Sep 05, 2018 at 05:38:57PM +0100, Mark Rutland wrote:
> In pmd_free_pte_page() and pud_free_pmd_page() we try to warn if they
> hit a present non-table entry. In both cases we'll warn for non-present
> entries, as the VM_WARN_ON() only checks the entry is not a table entry.
>
> This has been observed to result in warnings when booting a v4.19-rc2
> kernel under qemu.
>
> Fix this by bailing out earlier for non-present entries.
>
> Fixes: ec28bb9c9b0826d7 ("arm64: Implement page table free interfaces")
> Signed-off-by: Mark Rutland <mark.rutland@arm•com>
> Cc: Will Deacon <will.deacon@arm•com>
> Cc: Catalin Marinas <catalin.marinas@arm•com>
> ---
> arch/arm64/mm/mmu.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 65f86271f02b..8080c9f489c3 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -985,8 +985,9 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
>
> pmd = READ_ONCE(*pmdp);
>
> - /* No-op for empty entry and WARN_ON for valid entry */
> - if (!pmd_present(pmd) || !pmd_table(pmd)) {
> + if (!pmd_present(pmd))
> + return 1;
> + if (!pmd_table(pmd)) {
It's a pity this can't be written as:
if (!pmd_present(pmd) || VM_WARN_ON(!pmd_table(pmd)))
return 1;
and I suspect the fact that you can't do that with VM_WARN_ON actually
contributed to the bug in the first place.
Anywho, thanks for fixing it. I'll queue this up as a fix.
Will
prev parent reply other threads:[~2018-09-06 13:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-05 16:38 [PATCH] arm64: fix erroneous warnings in page freeing functions Mark Rutland
2018-09-06 13:52 ` Will Deacon [this message]
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