From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>
Cc: Stuart Yoder <stuyoder@gmail.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Vineeth Vijayan <vneethv@linux.ibm.com>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Andy Gross <agross@kernel.org>,
linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
NXP Linux Team <linux-imx@nxp.com>,
linux-arm-kernel@lists.infradead.org,
linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org,
linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org,
linux-arm-msm@vger.kernel.org, alsa-devel@alsa-project.org,
linux-spi@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Subject: [PATCH v7 01/12] driver: platform: Add helper for safer setting of driver_override
Date: Tue, 19 Apr 2022 13:34:24 +0200 [thread overview]
Message-ID: <20220419113435.246203-2-krzysztof.kozlowski@linaro.org> (raw)
In-Reply-To: <20220419113435.246203-1-krzysztof.kozlowski@linaro.org>
Several core drivers and buses expect that driver_override is a
dynamically allocated memory thus later they can kfree() it.
However such assumption is not documented, there were in the past and
there are already users setting it to a string literal. This leads to
kfree() of static memory during device release (e.g. in error paths or
during unbind):
kernel BUG at ../mm/slub.c:3960!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
...
(kfree) from [<c058da50>] (platform_device_release+0x88/0xb4)
(platform_device_release) from [<c0585be0>] (device_release+0x2c/0x90)
(device_release) from [<c0a69050>] (kobject_put+0xec/0x20c)
(kobject_put) from [<c0f2f120>] (exynos5_clk_probe+0x154/0x18c)
(exynos5_clk_probe) from [<c058de70>] (platform_drv_probe+0x6c/0xa4)
(platform_drv_probe) from [<c058b7ac>] (really_probe+0x280/0x414)
(really_probe) from [<c058baf4>] (driver_probe_device+0x78/0x1c4)
(driver_probe_device) from [<c0589854>] (bus_for_each_drv+0x74/0xb8)
(bus_for_each_drv) from [<c058b48c>] (__device_attach+0xd4/0x16c)
(__device_attach) from [<c058a638>] (bus_probe_device+0x88/0x90)
(bus_probe_device) from [<c05871fc>] (device_add+0x3dc/0x62c)
(device_add) from [<c075ff10>] (of_platform_device_create_pdata+0x94/0xbc)
(of_platform_device_create_pdata) from [<c07600ec>] (of_platform_bus_create+0x1a8/0x4fc)
(of_platform_bus_create) from [<c0760150>] (of_platform_bus_create+0x20c/0x4fc)
(of_platform_bus_create) from [<c07605f0>] (of_platform_populate+0x84/0x118)
(of_platform_populate) from [<c0f3c964>] (of_platform_default_populate_init+0xa0/0xb8)
(of_platform_default_populate_init) from [<c01031f8>] (do_one_initcall+0x8c/0x404)
Provide a helper which clearly documents the usage of driver_override.
This will allow later to reuse the helper and reduce the amount of
duplicated code.
Convert the platform driver to use a new helper and make the
driver_override field const char (it is not modified by the core).
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
drivers/base/driver.c | 69 +++++++++++++++++++++++++++++++++
drivers/base/platform.c | 28 ++-----------
include/linux/device/driver.h | 2 +
include/linux/platform_device.h | 6 ++-
4 files changed, 80 insertions(+), 25 deletions(-)
diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index 8c0d33e182fd..1b9d47b10bd0 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -30,6 +30,75 @@ static struct device *next_device(struct klist_iter *i)
return dev;
}
+/**
+ * driver_set_override() - Helper to set or clear driver override.
+ * @dev: Device to change
+ * @override: Address of string to change (e.g. &device->driver_override);
+ * The contents will be freed and hold newly allocated override.
+ * @s: NUL-terminated string, new driver name to force a match, pass empty
+ * string to clear it ("" or "\n", where the latter is only for sysfs
+ * interface).
+ * @len: length of @s
+ *
+ * Helper to set or clear driver override in a device, intended for the cases
+ * when the driver_override field is allocated by driver/bus code.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int driver_set_override(struct device *dev, const char **override,
+ const char *s, size_t len)
+{
+ const char *new, *old;
+ char *cp;
+
+ if (!override || !s)
+ return -EINVAL;
+
+ /*
+ * The stored value will be used in sysfs show callback (sysfs_emit()),
+ * which has a length limit of PAGE_SIZE and adds a trailing newline.
+ * Thus we can store one character less to avoid truncation during sysfs
+ * show.
+ */
+ if (len >= (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ if (!len) {
+ /* Empty string passed - clear override */
+ device_lock(dev);
+ old = *override;
+ *override = NULL;
+ device_unlock(dev);
+ kfree(old);
+
+ return 0;
+ }
+
+ cp = strnchr(s, len, '\n');
+ if (cp)
+ len = cp - s;
+
+ new = kstrndup(s, len, GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+
+ device_lock(dev);
+ old = *override;
+ if (cp != s) {
+ *override = new;
+ } else {
+ /* "\n" passed - clear override */
+ kfree(new);
+ *override = NULL;
+ }
+ device_unlock(dev);
+
+ kfree(old);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(driver_set_override);
+
/**
* driver_for_each_device - Iterator for devices bound to a driver.
* @drv: Driver we're iterating.
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 8cc272fd5c99..b684157b7f2f 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1275,31 +1275,11 @@ static ssize_t driver_override_store(struct device *dev,
const char *buf, size_t count)
{
struct platform_device *pdev = to_platform_device(dev);
- char *driver_override, *old, *cp;
-
- /* We need to keep extra room for a newline */
- if (count >= (PAGE_SIZE - 1))
- return -EINVAL;
-
- driver_override = kstrndup(buf, count, GFP_KERNEL);
- if (!driver_override)
- return -ENOMEM;
-
- cp = strchr(driver_override, '\n');
- if (cp)
- *cp = '\0';
-
- device_lock(dev);
- old = pdev->driver_override;
- if (strlen(driver_override)) {
- pdev->driver_override = driver_override;
- } else {
- kfree(driver_override);
- pdev->driver_override = NULL;
- }
- device_unlock(dev);
+ int ret;
- kfree(old);
+ ret = driver_set_override(dev, &pdev->driver_override, buf, count);
+ if (ret)
+ return ret;
return count;
}
diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h
index 15e7c5e15d62..700453017e1c 100644
--- a/include/linux/device/driver.h
+++ b/include/linux/device/driver.h
@@ -151,6 +151,8 @@ extern int __must_check driver_create_file(struct device_driver *driver,
extern void driver_remove_file(struct device_driver *driver,
const struct driver_attribute *attr);
+int driver_set_override(struct device *dev, const char **override,
+ const char *s, size_t len);
extern int __must_check driver_for_each_device(struct device_driver *drv,
struct device *start,
void *data,
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 7c96f169d274..582d83ed9a91 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -31,7 +31,11 @@ struct platform_device {
struct resource *resource;
const struct platform_device_id *id_entry;
- char *driver_override; /* Driver name to force a match */
+ /*
+ * Driver name to force a match. Do not set directly, because core
+ * frees it. Use driver_set_override() to set or clear it.
+ */
+ const char *driver_override;
/* MFD cell pointer */
struct mfd_cell *mfd_cell;
--
2.32.0
next prev parent reply other threads:[~2022-04-19 11:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-19 11:34 [PATCH v7 00/12] Fix broken usage of driver_override (and kfree of static memory) Krzysztof Kozlowski
2022-04-19 11:34 ` Krzysztof Kozlowski [this message]
2022-04-20 17:12 ` [PATCH v7 01/12] driver: platform: Add helper for safer setting of driver_override Rafael J. Wysocki
2022-04-19 11:34 ` [PATCH v7 02/12] amba: Use driver_set_override() instead of open-coding Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 03/12] fsl-mc: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 04/12] hv: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 05/12] PCI: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 06/12] s390/cio: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 07/12] spi: Use helper for safer setting of driver_override Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 08/12] vdpa: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 09/12] clk: imx: scu: Fix kfree() of static memory on setting driver_override Krzysztof Kozlowski
2022-04-23 16:09 ` Abel Vesa
2022-04-19 11:34 ` [PATCH v7 10/12] slimbus: qcom-ngd: " Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 11/12] rpmsg: Constify local variable in field store macro Krzysztof Kozlowski
2022-04-19 11:34 ` [PATCH v7 12/12] rpmsg: Fix kfree() of static memory on setting driver_override Krzysztof Kozlowski
[not found] ` <CGME20220429122942eucas1p1820d0cd17a871d4953bac2b3de1dcdd9@eucas1p1.samsung.com>
2022-04-29 12:29 ` Marek Szyprowski
2022-04-29 14:16 ` Krzysztof Kozlowski
2022-04-29 14:51 ` Marek Szyprowski
2022-04-29 18:29 ` Krzysztof Kozlowski
2022-04-20 9:20 ` [PATCH v7 00/12] Fix broken usage of driver_override (and kfree of static memory) Krzysztof Kozlowski
2022-04-22 14:54 ` Greg Kroah-Hartman
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