The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cf4a4493ff70874f8af26d75d4346c591c298e89 Mon Sep 17 00:00:00 2001 From: Peng Hao flyingpenghao@gmail.com Date: Wed, 22 Dec 2021 09:12:25 +0800 Subject: [PATCH] virtio/virtio_mem: handle a possible NULL as a memcpy parameter

There is a check for vm->sbm.sb_states before, and it should check it here as well.

Signed-off-by: Peng Hao flyingpeng@tencent.com Link: https://lore.kernel.org/r/20211222011225.40573-1-flyingpeng@tencent.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Fixes: 5f1f79bbc9e2 ("virtio-mem: Paravirtualized memory hotplug") Cc: stable@vger.kernel.org # v5.8+

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index a6a78685cfbe..38becd8d578c 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -593,7 +593,7 @@ static int virtio_mem_sbm_sb_states_prepare_next_mb(struct virtio_mem *vm) return -ENOMEM;

mutex_lock(&vm->hotplug_mutex); - if (new_bitmap) + if (vm->sbm.sb_states) memcpy(new_bitmap, vm->sbm.sb_states, old_pages * PAGE_SIZE);

old_bitmap = vm->sbm.sb_states;