From 4134455f2aafdfeab50cabb4cccb35e916034b93 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Tue, 9 Feb 2021 10:56:20 -0500
Subject: dm writecache: fix writing beyond end of underlying device when shrinking

From: Mikulas Patocka <mpatocka@redhat.com>

commit 4134455f2aafdfeab50cabb4cccb35e916034b93 upstream.

Do not attempt to write any data beyond the end of the underlying data
device while shrinking it.

The DM writecache device must be suspended when the underlying data
device is shrunk.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/md/dm-writecache.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -142,6 +142,7 @@ struct dm_writecache {
 	size_t metadata_sectors;
 	size_t n_blocks;
 	uint64_t seq_count;
+	sector_t data_device_sectors;
 	void *block_start;
 	struct wc_entry *entries;
 	unsigned block_size;
@@ -929,6 +930,8 @@ static void writecache_resume(struct dm_
 
 	wc_lock(wc);
 
+	wc->data_device_sectors = i_size_read(wc->dev->bdev->bd_inode) >> SECTOR_SHIFT;
+
 	if (WC_MODE_PMEM(wc)) {
 		persistent_memory_invalidate_cache(wc->memory_map, wc->memory_map_size);
 	} else {
@@ -1499,6 +1502,10 @@ static bool wc_add_block(struct writebac
 	void *address = memory_data(wc, e);
 
 	persistent_memory_flush_cache(address, block_size);
+
+	if (unlikely(bio_end_sector(&wb->bio) >= wc->data_device_sectors))
+		return true;
+
 	return bio_add_page(&wb->bio, persistent_memory_page(address),
 			    block_size, persistent_memory_page_offset(address)) != 0;
 }
@@ -1571,6 +1578,9 @@ static void __writecache_writeback_pmem(
 		if (writecache_has_error(wc)) {
 			bio->bi_status = BLK_STS_IOERR;
 			bio_endio(&wb->bio);
+		} else if (unlikely(!bio_sectors(&wb->bio))) {
+			bio->bi_status = BLK_STS_OK;
+			bio_endio(&wb->bio);
 		} else {
 			submit_bio(&wb->bio);
 		}
@@ -1614,6 +1624,14 @@ static void __writecache_writeback_ssd(s
 			e = f;
 		}
 
+		if (unlikely(to.sector + to.count > wc->data_device_sectors)) {
+			if (to.sector >= wc->data_device_sectors) {
+				writecache_copy_endio(0, 0, c);
+				continue;
+			}
+			from.count = to.count = wc->data_device_sectors - to.sector;
+		}
+
 		dm_kcopyd_copy(wc->dm_kcopyd, &from, 1, &to, 0, writecache_copy_endio, c);
 
 		__writeback_throttle(wc, wbl);