linux-kernel - Re: [PATCH V2 2/2] proc/kcore: Do not try to access unaccepted memory

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Message-ID: <3a37361d-1f3b-c283-3fb0-ab3614e3d38c@redhat.com>
Date:   Tue, 12 Sep 2023 09:13:04 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-coco@...ts.linux.dev, linux-efi@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH V2 2/2] proc/kcore: Do not try to access unaccepted memory

On 11.09.23 13:21, Adrian Hunter wrote:
> Support for unaccepted memory was added recently, refer commit
> dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby a virtual
> machine may need to accept memory before it can be used.
> 
> Do not try to access unaccepted memory because it can cause the guest to
> fail.
> 
> For /proc/kcore, which is read-only and does not support mmap, this means a
> read of unaccepted memory will return zeros.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>   fs/proc/kcore.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> 
> Changes in V2:
> 
>            Change patch subject and commit message
>            Do not open code pfn_is_unaccepted_memory()
> 
> 
> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> index 23fc24d16b31..6422e569b080 100644
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -546,7 +546,8 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
>   			 * and explicitly excluded physical ranges.
>   			 */
>   			if (!page || PageOffline(page) ||
> -			    is_page_hwpoison(page) || !pfn_is_ram(pfn)) {
> +			    is_page_hwpoison(page) || !pfn_is_ram(pfn) ||
> +			    pfn_is_unaccepted_memory(pfn)) {
>   				if (iov_iter_zero(tsz, iter) != tsz) {
>   					ret = -EFAULT;
>   					goto out;

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb