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?
Thanks,
Christian.
Signed-off-by: Chen Li <chenli@xxxxxxxxxxxxx>
---
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;
}
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