[Devel] [PATCH hci-8.1 v4 07/11] dm-ploop: take bat_lock around md page lookup in ploop_llseek_hole()

[Alexander Ivanov]

ploop_llseek_hole() walks the md pages tree without any lock, while
resize inserts new md pages into it in ploop_add_md_pages(). A lookup
racing with rb-tree rebalancing may follow a stale pointer or miss the
page and return -EINVAL.

https://virtuozzo.atlassian.net/browse/VSTOR-148171
Feature: dm-ploop: ploop target driver

Signed-off-by: Alexander Ivanov <alexander.ivanov at virtuozzo.com>
---
 drivers/md/dm-ploop-map.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 92ceadf41b42..691284a239df 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -2772,7 +2772,11 @@ loff_t ploop_llseek_hole(struct dm_target *ti, loff_t offset, int whence)
 	while (clu < READ_ONCE(ploop->nr_bat_entries)) {
 		if (id != ploop_bat_clu_to_page_nr(clu)) {
 			id = ploop_bat_clu_to_page_nr(clu);
+
+			spin_lock_irq(&ploop->bat_lock);
 			md = ploop_md_page_find(ploop, id);
+			spin_unlock_irq(&ploop->bat_lock);
+
 			if (!md)
 				return -EINVAL;
 		}
-- 
2.53.0