FAILED: patch "[PATCH] virtio/virtio_mem: handle a possible NULL as a memcpy" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

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;