[PATCH] drm: amdgpu: Use the correct size when allocating memory

[PATCH] drm: amdgpu: Use the correct size when allocating memory

[Christophe JAILLET]

When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
'sgt' (i.e struct sg_table), so this could lead to memory corruption.

Fixes: f44ffd677fb3 ("drm/amdgpu: add support for exporting VRAM using DMA-buf v3")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 134cc36e30c5..0739e259bf91 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -462,7 +462,7 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
 	unsigned int pages;
 	int i, r;
 
-	*sgt = kmalloc(sizeof(*sg), GFP_KERNEL);
+	*sgt = kmalloc(sizeof(**sgt), GFP_KERNEL);
 	if (!*sgt)
 		return -ENOMEM;
 
-- 
2.25.1

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Christian König]

Am 09.08.20 um 22:34 schrieb Christophe JAILLET:
> When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
>
> Fixes: f44ffd677fb3 ("drm/amdgpu: add support for exporting VRAM using DMA-buf v3")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Good catch, Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index 134cc36e30c5..0739e259bf91 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -462,7 +462,7 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
>   	unsigned int pages;
>   	int i, r;
>   
> -	*sgt = kmalloc(sizeof(*sg), GFP_KERNEL);
> +	*sgt = kmalloc(sizeof(**sgt), GFP_KERNEL);
>   	if (!*sgt)
>   		return -ENOMEM;
>   

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Dan Carpenter]

On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
> When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> 'sgt' (i.e struct sg_table), so this could lead to memory corruption.

The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
it won't lead to corruption.

    11  struct scatterlist {
    12          unsigned long   page_link;
    13          unsigned int    offset;
    14          unsigned int    length;
    15          dma_addr_t      dma_address;
    16  #ifdef CONFIG_NEED_SG_DMA_LENGTH
    17          unsigned int    dma_length;
    18  #endif
    19  };

    42  struct sg_table {
    43          struct scatterlist *sgl;        /* the list */
    44          unsigned int nents;             /* number of mapped entries */
    45          unsigned int orig_nents;        /* original size of list */
    46  };

regards,
dan carpenter

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Marion & Christophe JAILLET]

Le 10/08/2020 à 17:42, Dan Carpenter a écrit :
> On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
>> When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
>> of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
>> 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
> The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
> it won't lead to corruption.
>
>      11  struct scatterlist {
>      12          unsigned long   page_link;
>      13          unsigned int    offset;
>      14          unsigned int    length;
>      15          dma_addr_t      dma_address;
>      16  #ifdef CONFIG_NEED_SG_DMA_LENGTH
>      17          unsigned int    dma_length;
>      18  #endif
>      19  };
>
>      42  struct sg_table {
>      43          struct scatterlist *sgl;        /* the list */
>      44          unsigned int nents;             /* number of mapped entries */
>      45          unsigned int orig_nents;        /* original size of list */
>      46  };
>
> regards,
> dan carpenter


My bad. I read 'struct scatterlist sgl' (without the *)
Thanks for the follow-up, Dan.

Doesn't smatch catch such mismatch?
(I've not run smatch for a while, so it is maybe reported)

Well, the proposal is still valid, even if it has less impact as 
initially thought.

Thx for the review.

CJ

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Alex Deucher]

Applied and updated the commit message to reflect the sizes.

Thanks!

Alex

On Mon, Aug 10, 2020 at 3:07 PM Marion & Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
>
> Le 10/08/2020 à 17:42, Dan Carpenter a écrit :
> > On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
> >> When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> >> of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> >> 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
> > The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
> > it won't lead to corruption.
> >
> >      11  struct scatterlist {
> >      12          unsigned long   page_link;
> >      13          unsigned int    offset;
> >      14          unsigned int    length;
> >      15          dma_addr_t      dma_address;
> >      16  #ifdef CONFIG_NEED_SG_DMA_LENGTH
> >      17          unsigned int    dma_length;
> >      18  #endif
> >      19  };
> >
> >      42  struct sg_table {
> >      43          struct scatterlist *sgl;        /* the list */
> >      44          unsigned int nents;             /* number of mapped entries */
> >      45          unsigned int orig_nents;        /* original size of list */
> >      46  };
> >
> > regards,
> > dan carpenter
>
>
> My bad. I read 'struct scatterlist sgl' (without the *)
> Thanks for the follow-up, Dan.
>
> Doesn't smatch catch such mismatch?
> (I've not run smatch for a while, so it is maybe reported)
>
> Well, the proposal is still valid, even if it has less impact as
> initially thought.
>
> Thx for the review.
>
> CJ
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Dan Carpenter]

On Mon, Aug 10, 2020 at 08:41:14PM +0200, Marion & Christophe JAILLET wrote:
> 
> Le 10/08/2020 à 17:42, Dan Carpenter a écrit :
> > On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
> > > When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> > > of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> > > 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
> > The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
> > it won't lead to corruption.
> > 
> >      11  struct scatterlist {
> >      12          unsigned long   page_link;
> >      13          unsigned int    offset;
> >      14          unsigned int    length;
> >      15          dma_addr_t      dma_address;
> >      16  #ifdef CONFIG_NEED_SG_DMA_LENGTH
> >      17          unsigned int    dma_length;
> >      18  #endif
> >      19  };
> > 
> >      42  struct sg_table {
> >      43          struct scatterlist *sgl;        /* the list */
> >      44          unsigned int nents;             /* number of mapped entries */
> >      45          unsigned int orig_nents;        /* original size of list */
> >      46  };
> > 
> > regards,
> > dan carpenter
> 
> 
> My bad. I read 'struct scatterlist sgl' (without the *)
> Thanks for the follow-up, Dan.
> 
> Doesn't smatch catch such mismatch?
> (I've not run smatch for a while, so it is maybe reported)

That's why I was investigating it, because Smatch didn't catch it.

Smatch would have warned if it led to memory corruption.  Smatch also
tries to detect struct mismatches as a separate check but for some
reason it missed it.  I'm not totally sure why yet.  I suspect that it's
a complicated internal reason where Sparse is the sizeof to a normal
number...  It's a known issue and hard to fix.

> 
> Well, the proposal is still valid, even if it has less impact as initially
> thought.

Yep.

regards,
dan carpenter

Re: [PATCH] drm: amdgpu: Use the correct size when allocating memory

[Dan Carpenter]

On Tue, Aug 11, 2020 at 10:57:02AM +0300, Dan Carpenter wrote:
> On Mon, Aug 10, 2020 at 08:41:14PM +0200, Marion & Christophe JAILLET wrote:
> > 
> > Le 10/08/2020 à 17:42, Dan Carpenter a écrit :
> > > On Sun, Aug 09, 2020 at 10:34:06PM +0200, Christophe JAILLET wrote:
> > > > When '*sgt' is allocated, we must allocated 'sizeof(**sgt)' bytes instead
> > > > of 'sizeof(*sg)'. 'sg' (i.e. struct scatterlist) is smaller than
> > > > 'sgt' (i.e struct sg_table), so this could lead to memory corruption.
> > > The sizeof(*sg) is bigger than sizeof(**sgt) so this wastes memory but
> > > it won't lead to corruption.
> > > 
> > >      11  struct scatterlist {
> > >      12          unsigned long   page_link;
> > >      13          unsigned int    offset;
> > >      14          unsigned int    length;
> > >      15          dma_addr_t      dma_address;
> > >      16  #ifdef CONFIG_NEED_SG_DMA_LENGTH
> > >      17          unsigned int    dma_length;
> > >      18  #endif
> > >      19  };
> > > 
> > >      42  struct sg_table {
> > >      43          struct scatterlist *sgl;        /* the list */
> > >      44          unsigned int nents;             /* number of mapped entries */
> > >      45          unsigned int orig_nents;        /* original size of list */
> > >      46  };
> > > 
> > > regards,
> > > dan carpenter
> > 
> > 
> > My bad. I read 'struct scatterlist sgl' (without the *)
> > Thanks for the follow-up, Dan.
> > 
> > Doesn't smatch catch such mismatch?
> > (I've not run smatch for a while, so it is maybe reported)
> 
> That's why I was investigating it, because Smatch didn't catch it.
> 
> Smatch would have warned if it led to memory corruption.  Smatch also
> tries to detect struct mismatches as a separate check but for some
> reason it missed it.  I'm not totally sure why yet.  I suspect that it's
> a complicated internal reason where Sparse is the sizeof to a normal

s/is/changes/

> number...  It's a known issue and hard to fix.

regards,
dan carpenter