4.4-stable review patch. If anyone has any objections, please let me know.
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From: Sudeep Holla sudeep.holla@arm.com
[ Upstream commit 09bebb1adb21ecd04adf7ccb3b06f73e3a851e93 ]
Vexpress platforms provide two different restart handlers: SYS_REBOOT that restart the entire system, while DB_RESET only restarts the daughter board containing the CPU. DB_RESET is overridden by SYS_REBOOT if it exists.
notifier_chain_register used in register_restart_handler by design relies on notifiers to be registered once only, however vexpress restart notifier can get registered twice. When this happen it corrupts list of notifiers, as result some notifiers can be not called on proper event, traverse on list can be cycled forever, and second unregister can access already freed memory.
So far, since this was the only restart handler in the system, no issue was observed even if the same notifier was registered twice. However commit 6c5c0d48b686 ("watchdog: sp805: add restart handler") added support for SP805 restart handlers and since the system under test contains two vexpress restart and two SP805 watchdog instances, it was observed that during the boot traversing the restart handler list looped forever as there's a cycle in that list resulting in boot hang.
This patch fixes the issues by ensuring that the notifier is installed only once.
Cc: Sebastian Reichel sre@kernel.org Signed-off-by: Sudeep Holla sudeep.holla@arm.com Fixes: 46c99ac66222 ("power/reset: vexpress: Register with kernel restart handler") Signed-off-by: Sebastian Reichel sebastian.reichel@collabora.co.uk Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/power/reset/vexpress-poweroff.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/drivers/power/reset/vexpress-poweroff.c +++ b/drivers/power/reset/vexpress-poweroff.c @@ -35,6 +35,7 @@ static void vexpress_reset_do(struct dev }
static struct device *vexpress_power_off_device; +static atomic_t vexpress_restart_nb_refcnt = ATOMIC_INIT(0);
static void vexpress_power_off(void) { @@ -99,10 +100,13 @@ static int _vexpress_register_restart_ha int err;
vexpress_restart_device = dev; - err = register_restart_handler(&vexpress_restart_nb); - if (err) { - dev_err(dev, "cannot register restart handler (err=%d)\n", err); - return err; + if (atomic_inc_return(&vexpress_restart_nb_refcnt) == 1) { + err = register_restart_handler(&vexpress_restart_nb); + if (err) { + dev_err(dev, "cannot register restart handler (err=%d)\n", err); + atomic_dec(&vexpress_restart_nb_refcnt); + return err; + } } device_create_file(dev, &dev_attr_active);