Re: [PATCH] radeon: use kvcalloc for relocs and chunks

[Chen Li <chenli@uniontech.com>]

On Wed, 17 Mar 2021 17:19:11 +0800,
Chen Li wrote:
> 
> On Wed, 17 Mar 2021 15:55:47 +0800,
> Christian König wrote:
> > 
> > Am 17.03.21 um 07:22 schrieb Chen Li:
> > > kvmalloc_array + __GFP_ZERO is the same with kvcalloc.
> > > 
> > > As for p->chunks, it will be used in:
> > > ```
> > > if (ib_chunk->kdata)
> > > 		memcpy(parser->ib.ptr, ib_chunk->kdata, ib_chunk->length_dw * 4);
> > > ```
> > > 
> > > If chunks doesn't zero out with __GFP_ZERO, it may point to somewhere else, e.g.,
> > > ```
> > > Unable to handle kernel paging request at virtual address 0000000000010000
> > > ...
> > > pc is at memcpy+0x84/0x250
> > > ra is at radeon_cs_ioctl+0x368/0xb90 [radeon]
> > > ```
> > > 
> > > after allocating chunks with __GFP_KERNEL/kvcalloc, this bug is fixed.
> > 
> > NAK to zeroing the chunks array.
> > 
> > That array should be fully initialized with data before using it, otherwise we
> > have a much more serious bug and zeroing it out only papers over the real issue.
> > 
> > How did you trigger the NULL pointer deref above?
> 
> Hi, Christian, thanks for reply! From radeon_cs_parser_init:
> ```
> 	if (user_chunk.chunk_id == RADEON_CHUNK_ID_IB) {
> 			if (!p->rdev || !(p->rdev->flags & RADEON_IS_AGP))
> 
>             /****** chenli: chunks[0] come here and continue! ******/
> 
> 				continue;
> 		}
> 
> 		p->chunks[i].kdata = kvmalloc_array(size, sizeof(uint32_t), GFP_KERNEL);
> ```
> In my case, chunks[0] is not allocated because it is just get continued, so it's not
> wired that kdata in "memcpy(parser->ib.ptr, ib_chunk->kdata, ib_chunk->length_dw * 4);"
> trigger the invalid address. 
>         

By the ways, chunks were allocated with kcalloc before https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=3fcb4f01deedfa290e903e030956b8e1a5cb764f,
which do zero the chunks array, that's why this error never happen before.

> > 
> > Thanks,
> > Christian.
> > 
> > > Signed-off-by: Chen Li <chenli@uniontech.com>
> > > ---
> > >   drivers/gpu/drm/radeon/radeon_cs.c | 6 +++---
> > >   1 file changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/radeon/radeon_cs.c b/drivers/gpu/drm/radeon/radeon_cs.c
> > > index fb736ef9f9aa..059431689c2d 100644
> > > --- a/drivers/gpu/drm/radeon/radeon_cs.c
> > > +++ b/drivers/gpu/drm/radeon/radeon_cs.c
> > > @@ -93,8 +93,8 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
> > >   	p->dma_reloc_idx = 0;
> > >   	/* FIXME: we assume that each relocs use 4 dwords */
> > >   	p->nrelocs = chunk->length_dw / 4;
> > > -	p->relocs = kvmalloc_array(p->nrelocs, sizeof(struct radeon_bo_list),
> > > -			GFP_KERNEL | __GFP_ZERO);
> > > +	p->relocs = kvcalloc(p->nrelocs, sizeof(struct radeon_bo_list),
> > > +			GFP_KERNEL);
> > >   	if (p->relocs == NULL) {
> > >   		return -ENOMEM;
> > >   	}
> > > @@ -299,7 +299,7 @@ int radeon_cs_parser_init(struct radeon_cs_parser *p, void *data)
> > >   	}
> > >   	p->cs_flags = 0;
> > >   	p->nchunks = cs->num_chunks;
> > > -	p->chunks = kvmalloc_array(p->nchunks, sizeof(struct radeon_cs_chunk), GFP_KERNEL);
> > > +	p->chunks = kvcalloc(p->nchunks, sizeof(struct radeon_cs_chunk), GFP_KERNEL);
> > >   	if (p->chunks == NULL) {
> > >   		return -ENOMEM;
> > >   	}
> > 
> > 
> > 
> 
> Regards,
>   Chen Li
> 
> 

Regards,
  Chen Li


_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx