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

[Daniel Henrique Barboza <danielhb413@gmail.com>]

On 7/20/22 10:16, Greg Kurz wrote:
> 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>


Thanks Greg! I'll queue this up as an eligible fix for the soft freeze.


Daniel


> 
>> 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);
>