linux-kernel - [PATCH v2 1/2] mm: Call arch_swap_restore() from do_swap

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Message-Id: <20230516023514.2643054-2-pcc@google.com>
Date:   Mon, 15 May 2023 19:35:12 -0700
From:   Peter Collingbourne <pcc@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Peter Collingbourne <pcc@...gle.com>,
        "Qun-wei Lin (林群崴)" 
        <Qun-wei.Lin@...iatek.com>, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "surenb@...gle.com" <surenb@...gle.com>,
        "david@...hat.com" <david@...hat.com>,
        "Chinwen Chang (張錦文)" 
        <chinwen.chang@...iatek.com>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        "Kuan-Ying Lee (李冠穎)" 
        <Kuan-Ying.Lee@...iatek.com>,
        "Casper Li (李中榮)" 
        <casper.li@...iatek.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        vincenzo.frascino@....com,
        Alexandru Elisei <alexandru.elisei@....com>, will@...nel.org,
        eugenis@...gle.com, Steven Price <steven.price@....com>,
        stable@...r.kernel.org
Subject: [PATCH v2 1/2] mm: Call arch_swap_restore() from do_swap_page()

Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
the call to swap_free() before the call to set_pte_at(), which meant that
the MTE tags could end up being freed before set_pte_at() had a chance
to restore them. Fix it by adding a call to the arch_swap_restore() hook
before the call to swap_free().

Signed-off-by: Peter Collingbourne <pcc@...gle.com>
Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
Cc: <stable@...r.kernel.org> # 6.1
Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@...iatek.com>
Link: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@mediatek.com/
---
v2:
- Call arch_swap_restore() directly instead of via arch_do_swap_page()

 mm/memory.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 01a23ad48a04..a2d9e6952d31 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3914,6 +3914,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		}
 	}
 
+	/*
+	 * Some architectures may have to restore extra metadata to the page
+	 * when reading from swap. This metadata may be indexed by swap entry
+	 * so this must be called before swap_free().
+	 */
+	arch_swap_restore(entry, folio);
+
 	/*
 	 * Remove the swap entry and conditionally try to free up the swapcache.
 	 * We're already holding a reference on the page but haven't mapped it
-- 
2.40.1.606.ga4b1b128d6-goog