[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <2982a4f2-ea8f-4fa4-81ea-d73c00fc2ad0@suse.com>
Date: Sat, 29 Jun 2024 12:20:23 +0200
From: Jürgen Groß <jgross@...e.com>
To: Ashish Kalra <Ashish.Kalra@....com>, 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, mhklinux@...look.com, peterx@...hat.com,
linux-kernel@...r.kernel.org, thomas.lendacky@....com,
linux-coco@...ts.linux.dev, jroedel@...e.de
Subject: Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory
holes in direct mapping
On 28.06.24 22:52, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
>
> lookup_address_in_pgd_attr() at pte level it is simply returning
> pte_offset_kernel() and there does not seem to be a check for
> returning NULL if pte_none().
>
> Fix lookup_address_in_pgd_attr() to add check for pte_none()
> after pte_offset_kernel() and return NULL if it is true.
Please have a look at the comment above lookup_address(). You should not
break the documented behavior without verifying that no caller is relying
on the current behavior. If this is fine, please update the comment.
Juergen
>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
> arch/x86/mm/pat/set_memory.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 443a97e515c0..be8b5bf3bc3f 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -672,6 +672,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
> p4d_t *p4d;
> pud_t *pud;
> pmd_t *pmd;
> + pte_t *pte;
>
> *level = PG_LEVEL_256T;
> *nx = false;
> @@ -717,7 +718,11 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
> *nx |= pmd_flags(*pmd) & _PAGE_NX;
> *rw &= pmd_flags(*pmd) & _PAGE_RW;
>
> - return pte_offset_kernel(pmd, address);
> + pte = pte_offset_kernel(pmd, address);
> + if (pte_none(*pte))
> + return NULL;
> +
> + return pte;
> }
>
> /*
Powered by blists - more mailing lists