diff mbox series

swiotlb: fix phys_addr_t overflow warning

Message ID 20190617132946.2817440-1-arnd@arndb.de
State Accepted
Commit 9c106119f6538f65bdddb7948a157d90625effa7
Headers show
Series swiotlb: fix phys_addr_t overflow warning | expand

Commit Message

Arnd Bergmann June 17, 2019, 1:28 p.m. UTC 
On architectures that have a larger dma_addr_t than phys_addr_t,
the swiotlb_tbl_map_single() function truncates its return code
in the failure path, making it impossible to identify the error
later, as we compare to the original value:

kernel/dma/swiotlb.c:551:9: error: implicit conversion from 'dma_addr_t' (aka 'unsigned long long') to 'phys_addr_t' (aka 'unsigned int') changes value from 18446744073709551615 to 4294967295 [-Werror,-Wconstant-conversion]
        return DMA_MAPPING_ERROR;

Use an explicit typecast here to convert it to the narrower type,
and use the same expression in the error handling later.

Fixes: b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
I still think that reverting the original commit would have
provided clearer semantics for this corner case, but at least
this patch restores the correct behavior.
---
 drivers/xen/swiotlb-xen.c | 2 +-
 kernel/dma/swiotlb.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

-- 
2.20.0

Comments

Stefano Stabellini June 17, 2019, 4:13 p.m. UTC | #1 
On Mon, 17 Jun 2019, Arnd Bergmann wrote:
> On architectures that have a larger dma_addr_t than phys_addr_t,

> the swiotlb_tbl_map_single() function truncates its return code

> in the failure path, making it impossible to identify the error

> later, as we compare to the original value:

> 

> kernel/dma/swiotlb.c:551:9: error: implicit conversion from 'dma_addr_t' (aka 'unsigned long long') to 'phys_addr_t' (aka 'unsigned int') changes value from 18446744073709551615 to 4294967295 [-Werror,-Wconstant-conversion]

>         return DMA_MAPPING_ERROR;

> 

> Use an explicit typecast here to convert it to the narrower type,

> and use the same expression in the error handling later.

> 

> Fixes: b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR")

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Acked-by: Stefano Stabellini <sstabellini@kernel.org>



> ---

> I still think that reverting the original commit would have

> provided clearer semantics for this corner case, but at least

> this patch restores the correct behavior.

> ---

>  drivers/xen/swiotlb-xen.c | 2 +-

>  kernel/dma/swiotlb.c      | 4 ++--

>  2 files changed, 3 insertions(+), 3 deletions(-)

> 

> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c

> index d53f3493a6b9..cfbe46785a3b 100644

> --- a/drivers/xen/swiotlb-xen.c

> +++ b/drivers/xen/swiotlb-xen.c

> @@ -402,7 +402,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,

>  

>  	map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir,

>  				     attrs);

> -	if (map == DMA_MAPPING_ERROR)

> +	if (map == (phys_addr_t)DMA_MAPPING_ERROR)

>  		return DMA_MAPPING_ERROR;

>  

>  	dev_addr = xen_phys_to_bus(map);

> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c

> index e906ef2e6315..a3be651973ad 100644

> --- a/kernel/dma/swiotlb.c

> +++ b/kernel/dma/swiotlb.c

> @@ -548,7 +548,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,

>  	if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())

>  		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",

>  			 size, io_tlb_nslabs, tmp_io_tlb_used);

> -	return DMA_MAPPING_ERROR;

> +	return (phys_addr_t)DMA_MAPPING_ERROR;

>  found:

>  	io_tlb_used += nslots;

>  	spin_unlock_irqrestore(&io_tlb_lock, flags);

> @@ -666,7 +666,7 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,

>  	/* Oh well, have to allocate and map a bounce buffer. */

>  	*phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start),

>  			*phys, size, dir, attrs);

> -	if (*phys == DMA_MAPPING_ERROR)

> +	if (*phys == (phys_addr_t)DMA_MAPPING_ERROR)

>  		return false;

>  

>  	/* Ensure that the address returned is DMA'ble */

> -- 

> 2.20.0

>
Konrad Rzeszutek Wilk June 19, 2019, 2:28 p.m. UTC | #2 
On Mon, Jun 17, 2019 at 09:13:16AM -0700, Stefano Stabellini wrote:
> On Mon, 17 Jun 2019, Arnd Bergmann wrote:

> > On architectures that have a larger dma_addr_t than phys_addr_t,

> > the swiotlb_tbl_map_single() function truncates its return code

> > in the failure path, making it impossible to identify the error

> > later, as we compare to the original value:

> > 

> > kernel/dma/swiotlb.c:551:9: error: implicit conversion from 'dma_addr_t' (aka 'unsigned long long') to 'phys_addr_t' (aka 'unsigned int') changes value from 18446744073709551615 to 4294967295 [-Werror,-Wconstant-conversion]

> >         return DMA_MAPPING_ERROR;

> > 

> > Use an explicit typecast here to convert it to the narrower type,

> > and use the same expression in the error handling later.

> > 

> > Fixes: b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR")

> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> 

> Acked-by: Stefano Stabellini <sstabellini@kernel.org>


queued.
> 

> 

> > ---

> > I still think that reverting the original commit would have

> > provided clearer semantics for this corner case, but at least

> > this patch restores the correct behavior.

> > ---

> >  drivers/xen/swiotlb-xen.c | 2 +-

> >  kernel/dma/swiotlb.c      | 4 ++--

> >  2 files changed, 3 insertions(+), 3 deletions(-)

> > 

> > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c

> > index d53f3493a6b9..cfbe46785a3b 100644

> > --- a/drivers/xen/swiotlb-xen.c

> > +++ b/drivers/xen/swiotlb-xen.c

> > @@ -402,7 +402,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,

> >  

> >  	map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir,

> >  				     attrs);

> > -	if (map == DMA_MAPPING_ERROR)

> > +	if (map == (phys_addr_t)DMA_MAPPING_ERROR)

> >  		return DMA_MAPPING_ERROR;

> >  

> >  	dev_addr = xen_phys_to_bus(map);

> > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c

> > index e906ef2e6315..a3be651973ad 100644

> > --- a/kernel/dma/swiotlb.c

> > +++ b/kernel/dma/swiotlb.c

> > @@ -548,7 +548,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,

> >  	if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())

> >  		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",

> >  			 size, io_tlb_nslabs, tmp_io_tlb_used);

> > -	return DMA_MAPPING_ERROR;

> > +	return (phys_addr_t)DMA_MAPPING_ERROR;

> >  found:

> >  	io_tlb_used += nslots;

> >  	spin_unlock_irqrestore(&io_tlb_lock, flags);

> > @@ -666,7 +666,7 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,

> >  	/* Oh well, have to allocate and map a bounce buffer. */

> >  	*phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start),

> >  			*phys, size, dir, attrs);

> > -	if (*phys == DMA_MAPPING_ERROR)

> > +	if (*phys == (phys_addr_t)DMA_MAPPING_ERROR)

> >  		return false;

> >  

> >  	/* Ensure that the address returned is DMA'ble */

> > -- 

> > 2.20.0

> >
diff mbox series

Patch

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index d53f3493a6b9..cfbe46785a3b 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -402,7 +402,7 @@  static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 
 	map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir,
 				     attrs);
-	if (map == DMA_MAPPING_ERROR)
+	if (map == (phys_addr_t)DMA_MAPPING_ERROR)
 		return DMA_MAPPING_ERROR;
 
 	dev_addr = xen_phys_to_bus(map);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index e906ef2e6315..a3be651973ad 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -548,7 +548,7 @@  phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 	if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())
 		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",
 			 size, io_tlb_nslabs, tmp_io_tlb_used);
-	return DMA_MAPPING_ERROR;
+	return (phys_addr_t)DMA_MAPPING_ERROR;
 found:
 	io_tlb_used += nslots;
 	spin_unlock_irqrestore(&io_tlb_lock, flags);
@@ -666,7 +666,7 @@  bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 	/* Oh well, have to allocate and map a bounce buffer. */
 	*phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start),
 			*phys, size, dir, attrs);
-	if (*phys == DMA_MAPPING_ERROR)
+	if (*phys == (phys_addr_t)DMA_MAPPING_ERROR)
 		return false;
 
 	/* Ensure that the address returned is DMA'ble */