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    SubjectRe: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node
    On Fri, Apr 27, 2018 at 11:45:02AM -0400, Kevin Easton wrote:
    > The struct vhost_msg within struct vhost_msg_node is copied to userspace,
    > so it should be allocated with kzalloc() to ensure all structure padding
    > is zeroed.
    >
    > Signed-off-by: Kevin Easton <kevin@guarana.org>
    > Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com
    > ---
    > drivers/vhost/vhost.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
    > index f3bd8e9..1b84dcff 100644
    > --- a/drivers/vhost/vhost.c
    > +++ b/drivers/vhost/vhost.c
    > @@ -2339,7 +2339,7 @@ EXPORT_SYMBOL_GPL(vhost_disable_notify);
    > /* Create a new message. */
    > struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
    > {
    > - struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
    > + struct vhost_msg_node *node = kzalloc(sizeof *node, GFP_KERNEL);
    > if (!node)
    > return NULL;
    > node->vq = vq;


    Let's just init the msg though.

    OK it seems this is the best we can do for now,
    we need a new feature bit to fix it for 32 bit
    userspace on 64 bit kernels.

    Does the following help?

    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

    diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
    index f3bd8e9..58d9aec 100644
    --- a/drivers/vhost/vhost.c
    +++ b/drivers/vhost/vhost.c
    @@ -2342,6 +2342,9 @@ struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
    struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
    if (!node)
    return NULL;
    +
    + /* Make sure all padding within the structure is initialized. */
    + memset(&node->msg, 0, sizeof node->msg);
    node->vq = vq;
    node->msg.type = type;
    return node;
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