Re: [PATCH 1/3] dma-direct: provide the ability to reserve per-numa CMA

[Dan Carpenter]

Hi Barry,

url:    https://github.com/0day-ci/linux/commits/Barry-Song/support-per-numa-CMA-for-ARM-server/20200603-104821
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: x86_64-randconfig-m001-20200603 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

smatch warnings:
kernel/dma/contiguous.c:274 dma_alloc_contiguous() warn: variable dereferenced before check 'dev' (see line 272)

# https://github.com/0day-ci/linux/commit/adb919e972c1cac3d8b11905d5258d23d3aac6a4
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout adb919e972c1cac3d8b11905d5258d23d3aac6a4
vim +/dev +274 kernel/dma/contiguous.c

b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  267  struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  268  {
90ae409f9eb3bc kernel/dma/contiguous.c       Christoph Hellwig 2019-08-20  269  	size_t count = size >> PAGE_SHIFT;
b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  270  	struct page *page = NULL;
bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  271  	struct cma *cma = NULL;
adb919e972c1ca kernel/dma/contiguous.c       Barry Song        2020-06-03 @272  	int nid = dev_to_node(dev);
                                                                                                              ^^^
Dereferenced inside function.

bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  273  
bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23 @274  	if (dev && dev->cma_area)
                                                                                            ^^^
Too late.

bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  275  		cma = dev->cma_area;
adb919e972c1ca kernel/dma/contiguous.c       Barry Song        2020-06-03  276  	else if ((nid != NUMA_NO_NODE) && dma_contiguous_pernuma_area[nid]
adb919e972c1ca kernel/dma/contiguous.c       Barry Song        2020-06-03  277  		&& !(gfp & (GFP_DMA | GFP_DMA32)))
adb919e972c1ca kernel/dma/contiguous.c       Barry Song        2020-06-03  278  		cma = dma_contiguous_pernuma_area[nid];
bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  279  	else if (count > 1)
bd2e75633c8012 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  280  		cma = dma_contiguous_default_area;
b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  281  
b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  282  	/* CMA can be used only in the context which permits sleeping */
b1d2dc009dece4 kernel/dma/contiguous.c       Nicolin Chen      2019-05-23  283  	if (cma && gfpflags_allow_blocking(gfp)) {

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