From: Dan Carpenter <error27@gmail.com>
Date: Tue, 15 Nov 2022 16:16:43 +0300
Subject: drbd: use after free in drbd_create_device()
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Git-commit: a7a1598189228b5007369a9622ccdf587be0730f
Patch-mainline: v6.1-rc6
References: git-fixes

The drbd_destroy_connection() frees the "connection" so use the _safe()
iterator to prevent a use after free.

Fixes: b6f85ef9538b ("drbd: Iterate over all connections")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Link: https://lore.kernel.org/r/Y3Jd5iZRbNQ9w6gm@kili
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Lee Duncan <lduncan@suse.com>
---
 drivers/block/drbd/drbd_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index f3e4db16fd07..8532b839a343 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2672,7 +2672,7 @@ static int init_submitter(struct drbd_device *device)
 enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsigned int minor)
 {
 	struct drbd_resource *resource = adm_ctx->resource;
-	struct drbd_connection *connection;
+	struct drbd_connection *connection, *n;
 	struct drbd_device *device;
 	struct drbd_peer_device *peer_device, *tmp_peer_device;
 	struct gendisk *disk;
@@ -2789,7 +2789,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	return NO_ERROR;
 
 out_idr_remove_from_resource:
-	for_each_connection(connection, resource) {
+	for_each_connection_safe(connection, n, resource) {
 		peer_device = idr_remove(&connection->peer_devices, vnr);
 		if (peer_device)
 			kref_put(&connection->kref, drbd_destroy_connection);