linux-kernel - [PATCH] driver core: platform: Fix the usage of platform device name(pdev->name)

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Date:   Mon, 22 Apr 2019 17:16:29 -0700
From:   Venkata Narendra Kumar Gutta <vnkgutta@...eaurora.org>
To:     gregkh@...uxfoundation.org, davem@...emloft.net,
        alexander.deucher@....com, tsoni@...eaurora.org,
        psodagud@...eaurora.org, jshriram@...eaurora.org,
        vnkgutta@...eaurora.org, linux-kernel@...r.kernel.org
Subject: [PATCH] driver core: platform: Fix the usage of platform device name(pdev->name)

Platform core is using pdev->name as the platform device name to do
the binding of the devices with the drivers. But, when the platform
driver overrides the platform device name with dev_set_name(),
the pdev->name is pointing to a location which is freed and becomes
an invalid parameter to do the binding match.

use-after-free instance:

[   33.325013] BUG: KASAN: use-after-free in strcmp+0x8c/0xb0
[   33.330646] Read of size 1 at addr ffffffc10beae600 by task modprobe
[   33.339068] CPU: 5 PID: 518 Comm: modprobe Tainted:
			G S      W  O      4.19.30+ #3
[   33.346835] Hardware name: MTP (DT)
[   33.350419] Call trace:
[   33.352941]  dump_backtrace+0x0/0x3b8
[   33.356713]  show_stack+0x24/0x30
[   33.360119]  dump_stack+0x160/0x1d8
[   33.363709]  print_address_description+0x84/0x2e0
[   33.368549]  kasan_report+0x26c/0x2d0
[   33.372322]  __asan_report_load1_noabort+0x2c/0x38
[   33.377248]  strcmp+0x8c/0xb0
[   33.380306]  platform_match+0x70/0x1f8
[   33.384168]  __driver_attach+0x78/0x3a0
[   33.388111]  bus_for_each_dev+0x13c/0x1b8
[   33.392237]  driver_attach+0x4c/0x58
[   33.395910]  bus_add_driver+0x350/0x560
[   33.399854]  driver_register+0x23c/0x328
[   33.403886]  __platform_driver_register+0xd0/0xe0

So, use dev_name(&pdev->dev), which fetches the platform device name from
the kobject(dev->kobj->name) of the device instead of the pdev->name.

Signed-off-by: Venkata Narendra Kumar Gutta <vnkgutta@...eaurora.org>
---
 drivers/base/platform.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index dab0a5a..0e23aa2 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -888,7 +888,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
 	if (len != -ENODEV)
 		return len;
 
-	len = snprintf(buf, PAGE_SIZE, "platform:%s\n", pdev->name);
+	len = snprintf(buf, PAGE_SIZE, "platform:%s\n", dev_name(&pdev->dev));
 
 	return (len >= PAGE_SIZE) ? (PAGE_SIZE - 1) : len;
 }
@@ -964,7 +964,7 @@ static int platform_uevent(struct device *dev, struct kobj_uevent_env *env)
 		return rc;
 
 	add_uevent_var(env, "MODALIAS=%s%s", PLATFORM_MODULE_PREFIX,
-			pdev->name);
+			dev_name(&pdev->dev));
 	return 0;
 }
 
@@ -973,7 +973,7 @@ static const struct platform_device_id *platform_match_id(
 			struct platform_device *pdev)
 {
 	while (id->name[0]) {
-		if (strcmp(pdev->name, id->name) == 0) {
+		if (strcmp(dev_name(&pdev->dev), id->name) == 0) {
 			pdev->id_entry = id;
 			return id;
 		}
@@ -1017,7 +1017,7 @@ static int platform_match(struct device *dev, struct device_driver *drv)
 		return platform_match_id(pdrv->id_table, pdev) != NULL;
 
 	/* fall-back to driver name match */
-	return (strcmp(pdev->name, drv->name) == 0);
+	return (strcmp(dev_name(&pdev->dev), drv->name) == 0);
 }
 
 #ifdef CONFIG_PM_SLEEP
-- 
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