linux-kernel - [PATCH 5.19 053/192] driver core: fix driver_set

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Date:   Tue, 13 Sep 2022 16:02:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        stable <stable@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Huisong Li <lihuisong@...wei.com>
Subject: [PATCH 5.19 053/192] driver core: fix driver_set_override() issue with empty strings

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

commit 5666a274a6d54372d6b79b1f78682a9d827e679e upstream.

Python likes to send an empty string for some sysfs files, including the
driver_override field.  When commit 23d99baf9d72 ("PCI: Use
driver_set_override() instead of open-coding") moved the PCI core to use
the driver core function instead of hand-rolling their own handler, this
showed up as a regression from some userspace tools, like DPDK.

Fix this up by actually looking at the length of the string first
instead of trusting that userspace got it correct.

Fixes: 23d99baf9d72 ("PCI: Use driver_set_override() instead of open-coding")
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: stable <stable@...nel.org>
Reported-by: Stephen Hemminger <stephen@...workplumber.org>
Tested-by: Huisong Li <lihuisong@...wei.com>
Reviewed-by: Stephen Hemminger <stephen@...workplumber.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Link: https://lore.kernel.org/r/20220901163734.3583106-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/base/driver.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -63,6 +63,12 @@ int driver_set_override(struct device *d
 	if (len >= (PAGE_SIZE - 1))
 		return -EINVAL;
 
+	/*
+	 * Compute the real length of the string in case userspace sends us a
+	 * bunch of \0 characters like python likes to do.
+	 */
+	len = strlen(s);
+
 	if (!len) {
 		/* Empty string passed - clear override */
 		device_lock(dev);