RE: [PATCH] RDMA/irdma: Fix a potential memory allocation issue in 'irdma_prm_add_pble_mem()'

["Saleem, Shiraz" <shiraz.saleem@intel.com>]

> Subject: Re: [PATCH] RDMA/irdma: Fix a potential memory allocation issue in
> 'irdma_prm_add_pble_mem()'
> 
> On Sun, Dec 05, 2021 at 09:17:24AM +0100, Christophe JAILLET wrote:
> > @@ -299,8 +298,7 @@ add_pble_prm(struct irdma_hmc_pble_rsrc *pble_rsrc)
> >  	return 0;
> >
> >  error:
> > -	if (chunk->bitmapbuf)
> > -		kfree(chunk->bitmapmem.va);
> > +	bitmap_free(chunk->bitmapbuf);
> >  	kfree(chunk->chunkmem.va);
> 
> Thanks for removing the "chunk->bitmapbuf = chunk->bitmapmem.va;" stuff.
> It was really confusing.  The kfree(chunk->chunkmem.va) is equivalent to
> kfree(chunk).  A good rule of thumb is that when you have one error:
> label to free everything then it's normally going to be buggy.
> 
> drivers/infiniband/hw/irdma/pble.c
>    281          pble_rsrc->next_fpm_addr += chunk->size;
>    282          ibdev_dbg(to_ibdev(dev),
>    283                    "PBLE: next_fpm_addr = %llx chunk_size[%llu] = 0x%llx\n",
>    284                    pble_rsrc->next_fpm_addr, chunk->size, chunk->size);
>    285          pble_rsrc->unallocated_pble -= (u32)(chunk->size >> 3);
>    286          list_add(&chunk->list, &pble_rsrc->pinfo.clist);
>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> "chunk" added to the "->pinfo.clist" list.
> 
>    287          sd_reg_val = (sd_entry_type == IRDMA_SD_TYPE_PAGED) ?
>    288                               sd_entry->u.pd_table.pd_page_addr.pa :
>    289                               sd_entry->u.bp.addr.pa;
>    290
>    291          if (!sd_entry->valid) {
>    292                  ret_code = irdma_hmc_sd_one(dev, hmc_info->hmc_fn_id,
> sd_reg_val,
>    293                                              idx->sd_idx, sd_entry->entry_type, true);
>    294                  if (ret_code)
>    295                          goto error;
>                                 ^^^^^^^^^^^
> 
>    296          }
>    297
>    298          sd_entry->valid = true;
>    299          return 0;
>    300
>    301  error:
>    302          if (chunk->bitmapbuf)
>    303                  kfree(chunk->bitmapmem.va);
>    304          kfree(chunk->chunkmem.va);
>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
> kfree(chunk) will lead to a use after free because it's still on the list.
> 

Ugh! Yes, this is a bug. I will send a separate fix out shortly for this one.

Shiraz