linux-kernel - [RFC 4/4] slimbus: ngd: Fix kfree() of const memory on setting driver

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Date:   Mon, 18 Feb 2019 11:16:00 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Russell King <linux@...linux.org.uk>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org
Subject: [RFC 4/4] slimbus: ngd: Fix kfree() of const memory on setting driver_override

Platform driver driver_override field should not be initialized from
const memory because the core later kfree() it.  If driver_override is
manually set later through sysfs, kfree() of old value leads to:

    $ echo "new_value" > /sys/bus/platform/drivers/.../driver_override

    kernel BUG at ../mm/slub.c:3960!
    Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
    ...
    (kfree) from [<c058e8c0>] (platform_set_driver_override+0x84/0xac)
    (platform_set_driver_override) from [<c058e908>] (driver_override_store+0x20/0x34)
    (driver_override_store) from [<c031f778>] (kernfs_fop_write+0x100/0x1dc)
    (kernfs_fop_write) from [<c0296de8>] (__vfs_write+0x2c/0x17c)
    (__vfs_write) from [<c02970c4>] (vfs_write+0xa4/0x188)
    (vfs_write) from [<c02972e8>] (ksys_write+0x4c/0xac)
    (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)

Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
---
 drivers/slimbus/qcom-ngd-ctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/slimbus/qcom-ngd-ctrl.c b/drivers/slimbus/qcom-ngd-ctrl.c
index 71f094c9ec68..fc46bf6ec903 100644
--- a/drivers/slimbus/qcom-ngd-ctrl.c
+++ b/drivers/slimbus/qcom-ngd-ctrl.c
@@ -1344,7 +1344,7 @@ static int of_qcom_slim_ngd_register(struct device *parent,
 		ngd->pdev = platform_device_alloc(QCOM_SLIM_NGD_DRV_NAME, id);
 		ngd->id = id;
 		ngd->pdev->dev.parent = parent;
-		ngd->pdev->driver_override = QCOM_SLIM_NGD_DRV_NAME;
+		platform_set_driver_override(ngd->pdev, QCOM_SLIM_NGD_DRV_NAME);
 		ngd->pdev->dev.of_node = node;
 		ctrl->ngd = ngd;
 		platform_set_drvdata(ngd->pdev, ctrl);
-- 
2.7.4