1 files changed, 16 insertions, 0 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index e1e621d0b6a0..59da2a415fbb 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1020,6 +1020,22 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 		goto fail;
 
 	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
+		/*
+		 * Having a local reference to the zswap entry doesn't exclude
+		 * swapping from invalidating and recycling the swap slot. Once
+		 * the swapcache is secured against concurrent swapping to and
+		 * from the slot, recheck that the entry is still current before
+		 * writing.
+		 */
+		spin_lock(&tree->lock);
+		if (zswap_rb_search(&tree->rbroot, entry->offset) != entry) {
+			spin_unlock(&tree->lock);
+			delete_from_swap_cache(page_folio(page));
+			ret = -ENOMEM;
+			goto fail;
+		}
+		spin_unlock(&tree->lock);
+
 		/* decompress */
 		acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
 		dlen = PAGE_SIZE;