Commit 6a7228d9 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman

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 62655397 ("driver core: platform: fix race
condition with driver_override") and 9561475d ("PCI: Fix race
condition with driver_override").

Fixes: 3cf38571 ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'")
Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: default avatarTodd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5f536246
...@@ -69,8 +69,12 @@ static ssize_t driver_override_show(struct device *_dev, ...@@ -69,8 +69,12 @@ static ssize_t driver_override_show(struct device *_dev,
struct device_attribute *attr, char *buf) struct device_attribute *attr, char *buf)
{ {
struct amba_device *dev = to_amba_device(_dev); 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, static ssize_t driver_override_store(struct device *_dev,
...@@ -78,7 +82,7 @@ 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) const char *buf, size_t count)
{ {
struct amba_device *dev = to_amba_device(_dev); 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 */ /* We need to keep extra room for a newline */
if (count >= (PAGE_SIZE - 1)) if (count >= (PAGE_SIZE - 1))
...@@ -92,12 +96,15 @@ static ssize_t driver_override_store(struct device *_dev, ...@@ -92,12 +96,15 @@ static ssize_t driver_override_store(struct device *_dev,
if (cp) if (cp)
*cp = '\0'; *cp = '\0';
device_lock(_dev);
old = dev->driver_override;
if (strlen(driver_override)) { if (strlen(driver_override)) {
dev->driver_override = driver_override; dev->driver_override = driver_override;
} else { } else {
kfree(driver_override); kfree(driver_override);
dev->driver_override = NULL; dev->driver_override = NULL;
} }
device_unlock(_dev);
kfree(old); kfree(old);
......
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