Re: [Qemu-ppc] [Qemu-devel] [for-2.11 PATCH 03/26] spapr_iommu: use g_strdup_printf() instead of snprintf()

[Alexey Kardashevskiy]

On 26/07/17 03:58, Greg Kurz wrote:
> Passing a stack allocated buffer of arbitrary length to snprintf()
> without checking the return value can cause the resultant strings
> to be silently truncated.

The strings it is touching cannot be silently truncated as
"tce-iommu-XXXXXXXX" are shorter than 32 chars.


> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/ppc/spapr_iommu.c |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index e614621a8317..740d42608b61 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -252,17 +252,19 @@ static int spapr_tce_table_realize(DeviceState *dev)
>  {
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(dev);
>      Object *tcetobj = OBJECT(tcet);
> -    char tmp[32];
> +    gchar *tmp;
>  
>      tcet->fd = -1;
>      tcet->need_vfio = false;
> -    snprintf(tmp, sizeof(tmp), "tce-root-%x", tcet->liobn);
> +    tmp = g_strdup_printf("tce-root-%x", tcet->liobn);
>      memory_region_init(&tcet->root, tcetobj, tmp, UINT64_MAX);
> +    g_free(tmp);
>  
> -    snprintf(tmp, sizeof(tmp), "tce-iommu-%x", tcet->liobn);
> +    tmp = g_strdup_printf("tce-iommu-%x", tcet->liobn);
>      memory_region_init_iommu(&tcet->iommu, sizeof(tcet->iommu),
>                               TYPE_SPAPR_IOMMU_MEMORY_REGION,
>                               tcetobj, tmp, 0);
> +    g_free(tmp);
>  
>      QLIST_INSERT_HEAD(&spapr_tce_tables, tcet, list);
>  
> @@ -307,7 +309,7 @@ void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool 
> need_vfio)
>  sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn)
>  {
>      sPAPRTCETable *tcet;
> -    char tmp[32];
> +    gchar *tmp;
>  
>      if (spapr_tce_find_by_liobn(liobn)) {
>          error_report("Attempted to create TCE table with duplicate"
> @@ -318,8 +320,9 @@ sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, 
> uint32_t liobn)
>      tcet = SPAPR_TCE_TABLE(object_new(TYPE_SPAPR_TCE_TABLE));
>      tcet->liobn = liobn;
>  
> -    snprintf(tmp, sizeof(tmp), "tce-table-%x", liobn);
> +    tmp = g_strdup_printf("tce-table-%x", liobn);
>      object_property_add_child(OBJECT(owner), tmp, OBJECT(tcet), NULL);
> +    g_free(tmp);
>  
>      object_property_set_bool(OBJECT(tcet), true, "realized", NULL);
>  
> 
> 


-- 
Alexey