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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiaomeng Tong <xiam0nd.tong@gmail.com>,
        =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= 
        <christoph.boehmwalder@linbit.com>,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 5.16 240/285] drbd: fix an invalid memory access caused by incorrect use of list iterator
Date:   Tue, 12 Apr 2022 08:31:37 +0200
Message-Id: <20220412062950.589685667@linuxfoundation.org>
In-Reply-To: <20220412062943.670770901@linuxfoundation.org>
References: <20220412062943.670770901@linuxfoundation.org>
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From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

commit ae4d37b5df749926891583d42a6801b5da11e3c1 upstream.

The bug is here:
	idr_remove(&connection->peer_devices, vnr);

If the previous for_each_connection() don't exit early (no goto hit
inside the loop), the iterator 'connection' after the loop will be a
bogus pointer to an invalid structure object containing the HEAD
(&resource->connections). As a result, the use of 'connection' above
will lead to a invalid memory access (including a possible invalid free
as idr_remove could call free_layer).

The original intention should have been to remove all peer_devices,
but the following lines have already done the work. So just remove
this line and the unneeded label, to fix this bug.

Cc: stable@vger.kernel.org
Fixes: c06ece6ba6f1b ("drbd: Turn connection->volumes into connection->peer_devices")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/block/drbd/drbd_main.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2791,12 +2791,12 @@ enum drbd_ret_code drbd_create_device(st
 
 	if (init_submitter(device)) {
 		err = ERR_NOMEM;
-		goto out_idr_remove_vol;
+		goto out_idr_remove_from_resource;
 	}
 
 	err = add_disk(disk);
 	if (err)
-		goto out_idr_remove_vol;
+		goto out_idr_remove_from_resource;
 
 	/* inherit the connection state */
 	device->state.conn = first_connection(resource)->cstate;
@@ -2810,8 +2810,6 @@ enum drbd_ret_code drbd_create_device(st
 	drbd_debugfs_device_add(device);
 	return NO_ERROR;
 
-out_idr_remove_vol:
-	idr_remove(&connection->peer_devices, vnr);
 out_idr_remove_from_resource:
 	for_each_connection(connection, resource) {
 		peer_device = idr_remove(&connection->peer_devices, vnr);