[PATCH 3/3] scsi: 3w-9xxx: rework lock timeouts

Arnd Bergmann
2017-11-10T15:59:17Z

The TW_IOCTL_GET_LOCK ioctl uses do_gettimeofday() to check whether
a lock has expired. This can misbehave due to a concurrent
settimeofday() call, as it is based on 'real' time, and it
will overflow in y2038 on 32-bit architectures, producing
unexpected results when used across the overflow time.

This changes it to using monotonic time, using ktime_get()
to simplify the code.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/scsi/3w-9xxx.c | 13 ++++++-------
drivers/scsi/3w-9xxx.h | 2 +-
2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
index b1c9bd9c1bfd..b42c9c479d4b 100644
--- a/drivers/scsi/3w-9xxx.c
+++ b/drivers/scsi/3w-9xxx.c
@@ -645,8 +645,7 @@ static long twa_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
TW_Command_Full *full_command_packet;
TW_Compatibility_Info *tw_compat_info;
TW_Event *event;
- struct timeval current_time;
- u32 current_time_ms;
+ ktime_t current_time;
TW_Device_Extension *tw_dev = twa_device_extension_list[iminor(inode)];
int retval = TW_IOCTL_ERROR_OS_EFAULT;
void __user *argp = (void __user *)arg;
@@ -837,17 +836,17 @@ static long twa_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
break;
case TW_IOCTL_GET_LOCK:
tw_lock = (TW_Lock *)tw_ioctl->data_buffer;
- do_gettimeofday(&current_time);
- current_time_ms = (current_time.tv_sec * 1000) + (current_time.tv_usec / 1000);
+ current_time = ktime_get();

- if ((tw_lock->force_flag == 1) || (tw_dev->ioctl_sem_lock == 0) || (current_time_ms >= tw_dev->ioctl_msec)) {
+ if ((tw_lock->force_flag == 1) || (tw_dev->ioctl_sem_lock == 0) ||
+ ktime_after(current_time, tw_dev->ioctl_time)) {
tw_dev->ioctl_sem_lock = 1;
- tw_dev->ioctl_msec = current_time_ms + tw_lock->timeout_msec;
+ tw_dev->ioctl_time = ktime_add_ms(current_time, tw_lock->timeout_msec);
tw_ioctl->driver_command.status = 0;
tw_lock->time_remaining_msec = tw_lock->timeout_msec;
} else {
tw_ioctl->driver_command.status = TW_IOCTL_ERROR_STATUS_LOCKED;
- tw_lock->time_remaining_msec = tw_dev->ioctl_msec - current_time_ms;
+ tw_lock->time_remaining_msec = ktime_ms_delta(tw_dev->ioctl_time, current_time);
}
break;
case TW_IOCTL_RELEASE_LOCK:
diff --git a/drivers/scsi/3w-9xxx.h b/drivers/scsi/3w-9xxx.h
index b6c208cc474f..d88cd3499bd5 100644
--- a/drivers/scsi/3w-9xxx.h
+++ b/drivers/scsi/3w-9xxx.h
@@ -666,7 +666,7 @@ typedef struct TAG_TW_Device_Extension {
unsigned char event_queue_wrapped;
unsigned int error_sequence_id;
int ioctl_sem_lock;
- u32 ioctl_msec;
+ ktime_t ioctl_time;
int chrdev_request_id;
wait_queue_head_t ioctl_wqueue;
struct mutex ioctl_lock;
--
2.9.0