[PATCH v4 1/3] mm: Call arch_swap_restore() from do_swap_page()

[Peter Collingbourne]

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@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
Cc: <stable@xxxxxxxxxxxxxxx> # 6.1
Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@xxxxxxxxxxxx/
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
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 f69fbc251198..fc25764016b3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3932,6 +3932,13 @@ 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
-- 
2.40.1.698.g37aff9b760-goog