[PATCH] nouveau/dmem: handle kcalloc() allocation failure

[Duoming Zhou]

The kcalloc() in nouveau_dmem_evict_chunk() will return null if
the physical memory has run out. As a result, if we dereference
src_pfns, dst_pfns or dma_addrs, the null pointer dereference bugs
will happen.

This patch uses stack variables to replace the kcalloc().

Fixes: 249881232e14 ("nouveau/dmem: evict device private memory during release")
Signed-off-by: Duoming Zhou <duom...@zju.edu.cn>
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c 
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 12feecf71e7..9a578262c6d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -374,13 +374,13 @@ static void
 nouveau_dmem_evict_chunk(struct nouveau_dmem_chunk *chunk)
 {
        unsigned long i, npages = range_len(&chunk->pagemap.range) >> 
PAGE_SHIFT;
-       unsigned long *src_pfns, *dst_pfns;
-       dma_addr_t *dma_addrs;
+       unsigned long src_pfns[npages], dst_pfns[npages];
+       dma_addr_t dma_addrs[npages];
        struct nouveau_fence *fence;
 
-       src_pfns = kcalloc(npages, sizeof(*src_pfns), GFP_KERNEL);
-       dst_pfns = kcalloc(npages, sizeof(*dst_pfns), GFP_KERNEL);
-       dma_addrs = kcalloc(npages, sizeof(*dma_addrs), GFP_KERNEL);
+       memset(src_pfns, 0, npages);
+       memset(dst_pfns, 0, npages);
+       memset(dma_addrs, 0, npages);
 
        migrate_device_range(src_pfns, chunk->pagemap.range.start >> PAGE_SHIFT,
                        npages);
@@ -406,11 +406,8 @@ nouveau_dmem_evict_chunk(struct nouveau_dmem_chunk *chunk)
        migrate_device_pages(src_pfns, dst_pfns, npages);
        nouveau_dmem_fence_done(&fence);
        migrate_device_finalize(src_pfns, dst_pfns, npages);
-       kfree(src_pfns);
-       kfree(dst_pfns);
        for (i = 0; i < npages; i++)
                dma_unmap_page(chunk->drm->dev->dev, dma_addrs[i], PAGE_SIZE, 
DMA_BIDIRECTIONAL);
-       kfree(dma_addrs);
 }
 
 void
-- 
2.17.1