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

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Date:   Mon, 11 Sep 2023 14:21:14 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "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: [PATCH V2 2/2] proc/kcore: Do not try to access unaccepted memory

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;
-- 
2.34.1