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Date:   Thu, 21 Sep 2023 13:00:45 -0400
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Message-ID: <20230921170045.4189251-1-bgeffon@google.com>
Subject: [PATCH] PM: hibernate: use __get_safe_page() rather than touching the list.
From:   Brian Geffon <bgeffon@google.com>
To:     "Rafael J . Wysocki" <rafael@kernel.org>
Cc:     Pavel Machek <pavel@ucw.cz>, Len Brown <len.brown@intel.com>,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Matthias Kaehlcke <mka@chromium.org>, stable@vger.kernel.org,
        Brian Geffon <bgeffon@google.com>
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Precedence: bulk

We found at least one situation where the safe pages list was empty and
get_buffer() would gladly try to use a NULL pointer.

Signed-off-by: Brian Geffon <bgeffon@google.com>
Fixes: 8357376 ("swsusp: Improve handling of highmem")
Cc: stable@vger.kernel.org

Change-Id: Ibb43a9b4ac5ff2d7e3021fdacc08e116650231e9
---
 kernel/power/snapshot.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 362e6bae5891..2dcb33248518 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -2544,8 +2544,9 @@ static void *get_highmem_page_buffer(struct page *page,
 		pbe->copy_page = pfn_to_page(pfn);
 	} else {
 		/* Copy of the page will be stored in normal memory */
-		kaddr = safe_pages_list;
-		safe_pages_list = safe_pages_list->next;
+		kaddr = __get_safe_page(ca->gfp_mask);
+		if (!kaddr)
+			return ERR_PTR(-ENOMEM);
 		pbe->copy_page = virt_to_page(kaddr);
 	}
 	pbe->next = highmem_pblist;
@@ -2747,8 +2748,9 @@ static void *get_buffer(struct memory_bitmap *bm, struct chain_allocator *ca)
 		return ERR_PTR(-ENOMEM);
 	}
 	pbe->orig_address = page_address(page);
-	pbe->address = safe_pages_list;
-	safe_pages_list = safe_pages_list->next;
+	pbe->address = __get_safe_page(ca->gfp_mask);
+	if (!pbe->address)
+		return ERR_PTR(-ENOMEM);
 	pbe->next = restore_pblist;
 	restore_pblist = pbe;
 	return pbe->address;
-- 
2.42.0.459.ge4e396fd5e-goog