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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Peng Hao <flyingpeng@tencent.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
Subject: [PATCH 5.15 067/846] virtio/virtio_mem: handle a possible NULL as a memcpy parameter
Date:   Mon, 24 Jan 2022 19:33:04 +0100
Message-Id: <20220124184103.280002812@linuxfoundation.org>
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From: Peng Hao <flyingpenghao@gmail.com>

commit cf4a4493ff70874f8af26d75d4346c591c298e89 upstream.

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+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/virtio/virtio_mem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -577,7 +577,7 @@ static int virtio_mem_sbm_sb_states_prep
 		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;