Re: [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation

[Stefan Hajnoczi]

On Wed, Dec 15, 2021 at 10:29:48PM +0000, Raphael Norwitz wrote:
> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> ---
>  subprojects/libvhost-user/libvhost-user.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/subprojects/libvhost-user/libvhost-user.c 
> b/subprojects/libvhost-user/libvhost-user.c
> index 787f4d2d4f..573212a83b 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -801,6 +801,12 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
>      VuDevRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS] = {};
>      VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
>  
> +    if (vmsg->fd_num != 1 ||
> +        vmsg->size != sizeof(vmsg->payload.memreg)) {
> +        vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
> +        return true;

Most vu_panic() callers return false to indicate that a reply does not
need to be sent. When the return value is true vu_dispatch() sends a
response, which we don't want.

Note that vu_dispatch() returns true (success) when the message handler
function returns false. The success/failure behavior should probably be
separated from the reply_requested behavior :(.

Anyway, returning false is probably appropriate here.

Stefan

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