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Subject[PATCH] driver core: platform: fix race condition with driver_override
The driver_override implementation is susceptible to race condition when
different threads are reading vs storing a different driver override.
Add locking to avoid race condition.

Fixes: 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'")
Cc: stable@vger.kernel.org
Signed-off-by: Adrian Salido <salidoa@google.com>
---
drivers/base/platform.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index c2456839214a..493e03fa0e07 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -866,7 +866,7 @@ 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 = pdev->driver_override, *cp;
+ char *driver_override, *old, *cp;

if (count > PATH_MAX)
return -EINVAL;
@@ -879,12 +879,15 @@ static ssize_t driver_override_store(struct device *dev,
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);

kfree(old);

@@ -895,8 +898,12 @@ static ssize_t driver_override_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct platform_device *pdev = to_platform_device(dev);
+ ssize_t len;

- return sprintf(buf, "%s\n", pdev->driver_override);
+ device_lock(dev);
+ len = sprintf(buf, "%s\n", pdev->driver_override);
+ device_unlock(dev);
+ return len;
}
static DEVICE_ATTR_RW(driver_override);

--
2.13.0.rc0.306.g87b477812d-goog
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