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ARM: amba: Fix race condition with driver_override 

The driver_override implementation is susceptible to a race condition
when different threads are reading vs storing a different driver
override.  Add locking to avoid this race condition.

Cfr. commits 6265539776 ("driver core: platform: fix race
condition with driver_override") and 9561475db6 ("PCI: Fix race
condition with driver_override").

Fixes: 3cf3857134 ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Geert Uytterhoeven 2018-04-10 15:21:44 +02:00 committed by Greg Kroah-Hartman
parent 5f53624662
commit 6a7228d90d
1 changed files with 9 additions and 2 deletions
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11
drivers/amba/bus.c
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@ -69,8 +69,12 @@ static ssize_t driver_override_show(struct device *_dev,
struct device_attribute *attr, char *buf)
{
struct amba_device *dev = to_amba_device(_dev);
ssize_t len;
return sprintf(buf, "%s\n", dev->driver_override);
device_lock(_dev);
len = sprintf(buf, "%s\n", dev->driver_override);
device_unlock(_dev);
return len;
}
static ssize_t driver_override_store(struct device *_dev,
@ -78,7 +82,7 @@ static ssize_t driver_override_store(struct device *_dev,
const char *buf, size_t count)
{
struct amba_device *dev = to_amba_device(_dev);
char *driver_override, *old = dev->driver_override, *cp;
char *driver_override, *old, *cp;
/* We need to keep extra room for a newline */
if (count >= (PAGE_SIZE - 1))
@ -92,12 +96,15 @@ static ssize_t driver_override_store(struct device *_dev,
if (cp)
*cp = '\0';
device_lock(_dev);
old = dev->driver_override;
if (strlen(driver_override)) {
dev->driver_override = driver_override;
} else {
kfree(driver_override);
dev->driver_override = NULL;
}
device_unlock(_dev);
kfree(old);