linux-kernel - [PATCH v2 2/2] clk: samsung: exynos5: Fix kfree() of const memory on setting driver

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Message-Id: <1550749552-8133-3-git-send-email-krzk@kernel.org>
Date:   Thu, 21 Feb 2019 12:45:52 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     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>,
        linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: [PATCH v2 2/2] clk: samsung: exynos5: 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)

The clk-exynos5-subcmu driver uses override only for the purpose of
creating meaningful names for children devices (matching names of power
domains, e.g. DISP, MFC).  The driver_override was not developed for
this purpose so just switch to default names of devices to fix the
issue.

Fixes: b06a532bf1fa ("clk: samsung: Add Exynos5 sub-CMU clock driver")
Cc: <stable@...r.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
---
 drivers/clk/samsung/clk-exynos5-subcmu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos5-subcmu.c b/drivers/clk/samsung/clk-exynos5-subcmu.c
index d07ef26bd052..8ae44b5db4c2 100644
--- a/drivers/clk/samsung/clk-exynos5-subcmu.c
+++ b/drivers/clk/samsung/clk-exynos5-subcmu.c
@@ -138,12 +138,11 @@ static int __init exynos5_clk_register_subcmu(struct device *parent,
 	struct platform_device *pdev;
 	int ret;
 
-	pdev = platform_device_alloc(info->pd_name, -1);
+	pdev = platform_device_alloc("exynos5-subcmu", PLATFORM_DEVID_AUTO);
 	if (!pdev)
 		return -ENOMEM;
 
 	pdev->dev.parent = parent;
-	pdev->driver_override = "exynos5-subcmu";
 	platform_set_drvdata(pdev, (void *)info);
 	of_genpd_add_device(&genpdspec, &pdev->dev);
 	ret = platform_device_add(pdev);
-- 
2.7.4