Re: [PATCH v2 1/1] hw/ppc: check if spapr_drc_index() returns NULL in spapr_nvdimm.c

[Greg Kurz]

On Sat,  9 Apr 2022 17:08:56 -0300
Daniel Henrique Barboza <danielhb413@gmail.com> wrote:

> spapr_nvdimm_flush_completion_cb() and flush_worker_cb() are using the
> DRC object returned by spapr_drc_index() without checking it for NULL.
> In this case we would be dereferencing a NULL pointer when doing
> SPAPR_NVDIMM(drc->dev) and PC_DIMM(drc->dev).
> 
> This can happen if, during a scm_flush(), the DRC object is wrongly
> freed/released (e.g. a bug in another part of the code).
> spapr_drc_index() would then return NULL in the callbacks.
> 
> Fixes: Coverity CID 1487108, 1487178
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  hw/ppc/spapr_nvdimm.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 

LGTM

Reviewed-by: Greg Kurz <groug@kaod.org>

> diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
> index c4c97da5de..04a64cada3 100644
> --- a/hw/ppc/spapr_nvdimm.c
> +++ b/hw/ppc/spapr_nvdimm.c
> @@ -447,9 +447,15 @@ static int flush_worker_cb(void *opaque)
>  {
>      SpaprNVDIMMDeviceFlushState *state = opaque;
>      SpaprDrc *drc = spapr_drc_by_index(state->drcidx);
> -    PCDIMMDevice *dimm = PC_DIMM(drc->dev);
> -    HostMemoryBackend *backend = MEMORY_BACKEND(dimm->hostmem);
> -    int backend_fd = memory_region_get_fd(&backend->mr);
> +    PCDIMMDevice *dimm;
> +    HostMemoryBackend *backend;
> +    int backend_fd;
> +
> +    g_assert(drc != NULL);
> +
> +    dimm = PC_DIMM(drc->dev);
> +    backend = MEMORY_BACKEND(dimm->hostmem);
> +    backend_fd = memory_region_get_fd(&backend->mr);
>  
>      if (object_property_get_bool(OBJECT(backend), "pmem", NULL)) {
>          MemoryRegion *mr = host_memory_backend_get_memory(dimm->hostmem);
> @@ -475,7 +481,11 @@ static void spapr_nvdimm_flush_completion_cb(void 
> *opaque, int hcall_ret)
>  {
>      SpaprNVDIMMDeviceFlushState *state = opaque;
>      SpaprDrc *drc = spapr_drc_by_index(state->drcidx);
> -    SpaprNVDIMMDevice *s_nvdimm = SPAPR_NVDIMM(drc->dev);
> +    SpaprNVDIMMDevice *s_nvdimm;
> +
> +    g_assert(drc != NULL);
> +
> +    s_nvdimm = SPAPR_NVDIMM(drc->dev);
>  
>      state->hcall_ret = hcall_ret;
>      QLIST_REMOVE(state, node);