hw/vfio/spapr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
Coverity detected an issue (CID 1421903) with potential call of clz64(0)
which returns 64 which make it do "<<" with a negative number.
This checks the mask and avoids undefined behaviour.
In practice pgsizes and memory_region_iommu_get_min_page_size() always
have some common page sizes and even if they did not, the resulting page
size would be 0x8000.0000.0000.0000 (gcc 9.2) and
ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
hw/vfio/spapr.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
index 33692fc86fd6..2900bd19417a 100644
--- a/hw/vfio/spapr.c
+++ b/hw/vfio/spapr.c
@@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
{
int ret = 0;
IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
- uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
+ uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
unsigned entries, bits_total, bits_per_level, max_levels;
struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
long rampagesize = qemu_minrampagesize();
@@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
if (pagesize > rampagesize) {
pagesize = rampagesize;
}
- pagesize = 1ULL << (63 - clz64(container->pgsizes &
- (pagesize | (pagesize - 1))));
+ pgmask = container->pgsizes & (pagesize | (pagesize - 1));
+ pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
if (!pagesize) {
error_report("Host doesn't support page size 0x%"PRIx64
", the supported mask is 0x%lx",
--
2.17.1
On 3/24/20 7:39 AM, Alexey Kardashevskiy wrote:
> Coverity detected an issue (CID 1421903) with potential call of clz64(0)
> which returns 64 which make it do "<<" with a negative number.
>
> This checks the mask and avoids undefined behaviour.
>
> In practice pgsizes and memory_region_iommu_get_min_page_size() always
> have some common page sizes and even if they did not, the resulting page
> size would be 0x8000.0000.0000.0000 (gcc 9.2) and
> ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> hw/vfio/spapr.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 33692fc86fd6..2900bd19417a 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
> {
> int ret = 0;
> IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
> + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
> unsigned entries, bits_total, bits_per_level, max_levels;
> struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> long rampagesize = qemu_minrampagesize();
> @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
> if (pagesize > rampagesize) {
> pagesize = rampagesize;
> }
> - pagesize = 1ULL << (63 - clz64(container->pgsizes &
> - (pagesize | (pagesize - 1))));
> + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
Is that ROUND_UP(container->pgsizes, pagesize)?
> + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
> if (!pagesize) {
> error_report("Host doesn't support page size 0x%"PRIx64
> ", the supported mask is 0x%lx",
>
On Tue, 24 Mar 2020 14:27:35 +0100
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
>
> On 3/24/20 7:39 AM, Alexey Kardashevskiy wrote:
> > Coverity detected an issue (CID 1421903) with potential call of clz64(0)
> > which returns 64 which make it do "<<" with a negative number.
> >
> > This checks the mask and avoids undefined behaviour.
> >
> > In practice pgsizes and memory_region_iommu_get_min_page_size() always
> > have some common page sizes and even if they did not, the resulting page
> > size would be 0x8000.0000.0000.0000 (gcc 9.2) and
> > ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
> >
> > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---
> > hw/vfio/spapr.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> > index 33692fc86fd6..2900bd19417a 100644
> > --- a/hw/vfio/spapr.c
> > +++ b/hw/vfio/spapr.c
> > @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
> > {
> > int ret = 0;
> > IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> > - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
> > + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
> > unsigned entries, bits_total, bits_per_level, max_levels;
> > struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> > long rampagesize = qemu_minrampagesize();
> > @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
> > if (pagesize > rampagesize) {
> > pagesize = rampagesize;
> > }
> > - pagesize = 1ULL << (63 - clz64(container->pgsizes &
> > - (pagesize | (pagesize - 1))));
> > + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
>
> Is that ROUND_UP(container->pgsizes, pagesize)?
>
This means we clip all page sizes greater than pagesize from
container->pgsizes... It doesn't look like ROUND_UP() semantics
to me.
> > + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
> > if (!pagesize) {
> > error_report("Host doesn't support page size 0x%"PRIx64
> > ", the supported mask is 0x%lx",
> >
>
>
On 3/24/20 3:30 PM, Greg Kurz wrote:
> On Tue, 24 Mar 2020 14:27:35 +0100
> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
>>
>>
>> On 3/24/20 7:39 AM, Alexey Kardashevskiy wrote:
>>> Coverity detected an issue (CID 1421903) with potential call of clz64(0)
>>> which returns 64 which make it do "<<" with a negative number.
>>>
>>> This checks the mask and avoids undefined behaviour.
>>>
>>> In practice pgsizes and memory_region_iommu_get_min_page_size() always
>>> have some common page sizes and even if they did not, the resulting page
>>> size would be 0x8000.0000.0000.0000 (gcc 9.2) and
>>> ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>> ---
>>> hw/vfio/spapr.c | 6 +++---
>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
>>> index 33692fc86fd6..2900bd19417a 100644
>>> --- a/hw/vfio/spapr.c
>>> +++ b/hw/vfio/spapr.c
>>> @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
>>> {
>>> int ret = 0;
>>> IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
>>> - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
>>> + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
>>> unsigned entries, bits_total, bits_per_level, max_levels;
>>> struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
>>> long rampagesize = qemu_minrampagesize();
>>> @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
>>> if (pagesize > rampagesize) {
>>> pagesize = rampagesize;
>>> }
>>> - pagesize = 1ULL << (63 - clz64(container->pgsizes &
>>> - (pagesize | (pagesize - 1))));
>>> + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
>>
>> Is that ROUND_UP(container->pgsizes, pagesize)?
>>
>
> This means we clip all page sizes greater than pagesize from
> container->pgsizes... It doesn't look like ROUND_UP() semantics
> to me.
Ah. Extracting it as a new function with meaningful name would help code
review :)
>
>>> + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
>>> if (!pagesize) {
>>> error_report("Host doesn't support page size 0x%"PRIx64
>>> ", the supported mask is 0x%lx",
>>>
>>
>>
>
On Tue, Mar 24, 2020 at 05:39:12PM +1100, Alexey Kardashevskiy wrote:
> Coverity detected an issue (CID 1421903) with potential call of clz64(0)
> which returns 64 which make it do "<<" with a negative number.
>
> This checks the mask and avoids undefined behaviour.
>
> In practice pgsizes and memory_region_iommu_get_min_page_size() always
> have some common page sizes and even if they did not, the resulting page
> size would be 0x8000.0000.0000.0000 (gcc 9.2) and
> ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Applied to ppc-for-5.1.
> ---
> hw/vfio/spapr.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 33692fc86fd6..2900bd19417a 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
> {
> int ret = 0;
> IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
> + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
> unsigned entries, bits_total, bits_per_level, max_levels;
> struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> long rampagesize = qemu_minrampagesize();
> @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
> if (pagesize > rampagesize) {
> pagesize = rampagesize;
> }
> - pagesize = 1ULL << (63 - clz64(container->pgsizes &
> - (pagesize | (pagesize - 1))));
> + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
> + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
> if (!pagesize) {
> error_report("Host doesn't support page size 0x%"PRIx64
> ", the supported mask is 0x%lx",
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
On Thu, 26 Mar 2020 at 00:39, David Gibson <david@gibson.dropbear.id.au> wrote: > > On Tue, Mar 24, 2020 at 05:39:12PM +1100, Alexey Kardashevskiy wrote: > > Coverity detected an issue (CID 1421903) with potential call of clz64(0) > > which returns 64 which make it do "<<" with a negative number. > > > > This checks the mask and avoids undefined behaviour. > > > > In practice pgsizes and memory_region_iommu_get_min_page_size() always > > have some common page sizes and even if they did not, the resulting page > > size would be 0x8000.0000.0000.0000 (gcc 9.2) and > > ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway. > > > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > > Applied to ppc-for-5.1. As a coverity-issue-fix it would be nice to have this in 5.0 unless you think it's particularly risky. thanks -- PMM
On Thu, Mar 26, 2020 at 11:21:47AM +0000, Peter Maydell wrote: > On Thu, 26 Mar 2020 at 00:39, David Gibson <david@gibson.dropbear.id.au> wrote: > > > > On Tue, Mar 24, 2020 at 05:39:12PM +1100, Alexey Kardashevskiy wrote: > > > Coverity detected an issue (CID 1421903) with potential call of clz64(0) > > > which returns 64 which make it do "<<" with a negative number. > > > > > > This checks the mask and avoids undefined behaviour. > > > > > > In practice pgsizes and memory_region_iommu_get_min_page_size() always > > > have some common page sizes and even if they did not, the resulting page > > > size would be 0x8000.0000.0000.0000 (gcc 9.2) and > > > ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway. > > > > > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > > > > Applied to ppc-for-5.1. > > As a coverity-issue-fix it would be nice to have this in > 5.0 unless you think it's particularly risky. In fact, I realized that shortly after and moved it. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
On Tue, 24 Mar 2020 17:39:12 +1100
Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
> Coverity detected an issue (CID 1421903) with potential call of clz64(0)
> which returns 64 which make it do "<<" with a negative number.
>
> This checks the mask and avoids undefined behaviour.
>
> In practice pgsizes and memory_region_iommu_get_min_page_size() always
> have some common page sizes and even if they did not, the resulting page
> size would be 0x8000.0000.0000.0000 (gcc 9.2) and
> ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
Reviewed-by: Greg Kurz <groug@kaod.org>
> hw/vfio/spapr.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 33692fc86fd6..2900bd19417a 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
> {
> int ret = 0;
> IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
> + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
> unsigned entries, bits_total, bits_per_level, max_levels;
> struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> long rampagesize = qemu_minrampagesize();
> @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
> if (pagesize > rampagesize) {
> pagesize = rampagesize;
> }
> - pagesize = 1ULL << (63 - clz64(container->pgsizes &
> - (pagesize | (pagesize - 1))));
> + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
> + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
> if (!pagesize) {
> error_report("Host doesn't support page size 0x%"PRIx64
> ", the supported mask is 0x%lx",
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