User can call submit IOCTL before alloc_gpfifo IOCTL and can easily cause a kernel panic. The fix checks for a valid gpfifo.mem before proceeding with the submitted work. Bug 1968309 Change-Id: I5c1fc6f52b25426cd45e58e8b2e0e5bc6aa0c32f Signed-off-by: Debarshi Dutta <ddutta@nvidia.com> Reviewed-on: https://git-master.nvidia.com/r/1584519 Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com> Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>