Subject: [PATCH net 1/3] devlink: hold region lock when flushing snapshots

From: Jakub Kicinski <[email-masked]>
Date: Wed, 14 Dec 2022 18:01:00 -0800

Netdevsim triggers a splat on reload, when it destroys regions
with snapshots pending:

  WARNING: CPU: 1 PID: 787 at net/core/devlink.c:6291 devlink_region_snapshot_del+0x12e/0x140
  CPU: 1 PID: 787 Comm: devlink Not tainted 6.1.0-07460-g7ae9888d6e1c #580
  RIP: 0010:devlink_region_snapshot_del+0x12e/0x140
  Call Trace:
   <TASK>
   devl_region_destroy+0x70/0x140
   nsim_dev_reload_down+0x2f/0x60 [netdevsim]
   devlink_reload+0x1f7/0x360
   devlink_nl_cmd_reload+0x6ce/0x860
   genl_family_rcv_msg_doit.isra.0+0x145/0x1c0

This is the locking assert in devlink_region_snapshot_del(),
we're supposed to be holding the region->snapshot_lock here.

Fixes: 2dec18ad826f ("net: devlink: remove region snapshots list dependency on devlink->lock")
Signed-off-by: Jakub Kicinski <[email-masked]>
---
CC: [email-masked]
---
 net/core/devlink.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 6004bd0ccee4..d2df30829083 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -11925,8 +11925,10 @@ void devl_region_destroy(struct devlink_region *region)
 	devl_assert_locked(devlink);
 
 	/* Free all snapshots of region */
+	mutex_lock(&region->snapshot_lock);
 	list_for_each_entry_safe(snapshot, ts, &region->snapshot_list, list)
 		devlink_region_snapshot_del(region, snapshot);
+	mutex_unlock(&region->snapshot_lock);
 
 	list_del(&region->list);
 	mutex_destroy(&region->snapshot_lock);
-- 
2.38.1