4.4-stable review patch. If anyone has any objections, please let me know.
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From: Geert Uytterhoeven geert+renesas@glider.be
commit 6a7228d90d42bcacfe38786756ba62762b91c20a upstream.
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 6265539776a0810b ("driver core: platform: fix race condition with driver_override") and 9561475db680f714 ("PCI: Fix race condition with driver_override").
Fixes: 3cf385713460eb2b ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/amba/bus.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/drivers/amba/bus.c +++ b/drivers/amba/bus.c @@ -68,8 +68,12 @@ static ssize_t driver_override_show(stru 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, @@ -77,7 +81,7 @@ static ssize_t driver_override_store(str 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;
if (count > PATH_MAX) return -EINVAL; @@ -90,12 +94,15 @@ static ssize_t driver_override_store(str 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);