linux-kernel - [PATCH 2/3] mcb: fix error handling in mcb_alloc

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Message-Id: <b2fa90594069aa3f61d4658603d922f097ce2bde.1623768541.git.johannes.thumshirn@wdc.com>
Date:   Tue, 15 Jun 2021 23:55:29 +0900
From:   Johannes Thumshirn <johannes.thumshirn@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Johannes Thumshirn <jth@...nel.org>
Subject: [PATCH 2/3] mcb: fix error handling in mcb_alloc_bus()

From: Dan Carpenter <dan.carpenter@...cle.com>

There are two bugs:
1) If ida_simple_get() fails then this code calls put_device(carrier)
   but we haven't yet called get_device(carrier) and probably that
   leads to a use after free.
2) After device_initialize() then we need to use put_device() to
   release the bus.  This will free the internal resources tied to the
   device and call mcb_free_bus() which will free the rest.

Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Johannes Thumshirn <jth@...nel.org>
---
 drivers/mcb/mcb-core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/mcb/mcb-core.c b/drivers/mcb/mcb-core.c
index 38fbb3b59873..38cc8340e817 100644
--- a/drivers/mcb/mcb-core.c
+++ b/drivers/mcb/mcb-core.c
@@ -277,8 +277,8 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 
 	bus_nr = ida_simple_get(&mcb_ida, 0, 0, GFP_KERNEL);
 	if (bus_nr < 0) {
-		rc = bus_nr;
-		goto err_free;
+		kfree(bus);
+		return ERR_PTR(bus_nr);
 	}
 
 	bus->bus_nr = bus_nr;
@@ -293,12 +293,12 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 	dev_set_name(&bus->dev, "mcb:%d", bus_nr);
 	rc = device_add(&bus->dev);
 	if (rc)
-		goto err_free;
+		goto err_put;
 
 	return bus;
-err_free:
-	put_device(carrier);
-	kfree(bus);
+
+err_put:
+	put_device(&bus->dev);
 	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL_NS_GPL(mcb_alloc_bus, MCB);
-- 
2.31.1