linux-kernel - mmc: core: fix possible use after free of host

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Date:   Wed, 17 Apr 2019 16:28:37 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Mathieu Malaterre <malat@...ian.org>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: mmc: core: fix possible use after free of host

In the function mmc_alloc_host, the function put_device is called to
release allocated resources when mmc_gpio_alloc fails. Finally, the
function pointed by host->class_dev.class->dev_release (i.e.,
mmc_host_classdev_release) is used to release resources including the
host structure. However, after put_device, host is used and released
again. Resulting in a use-after-free bug.

Fixes: 1ed21719448("mmc: core: fix error path in mmc_host_alloc")
Signed-off-by: Pan Bian <bianpan2016@....com>
---
 drivers/mmc/core/host.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 3a4402a..f8ac567 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -429,8 +429,6 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 
 	if (mmc_gpio_alloc(host)) {
 		put_device(&host->class_dev);
-		ida_simple_remove(&mmc_host_ida, host->index);
-		kfree(host);
 		return NULL;
 	}
 
-- 
2.7.4