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@intel.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;
-- 
2.34.1

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@intel.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@redhat.com>

-- 
Cheers,

David / dhildenb