[kbuild] Re: [PATCH 1/7] vfio: iommu_type1: Clear added dirty bit when unwind pin

[Dan Carpenter]

Hi Keqian,

url:    https://github.com/0day-ci/linux/commits/Keqian-Zhu/vfio-iommu_type1-Some-fixes-and-optimization/20201210-154322 
base:   https://github.com/awilliam/linux-vfio.git  next
config: x86_64-randconfig-m001-20201215 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp at intel.com>
Reported-by: Dan Carpenter <dan.carpenter at oracle.com>

smatch warnings:
drivers/vfio/vfio_iommu_type1.c:648 vfio_iommu_type1_pin_pages() warn: variable dereferenced before check 'iommu' (see line 640)

vim +/iommu +648 drivers/vfio/vfio_iommu_type1.c

a54eb55045ae9b3 Kirti Wankhede  2016-11-17  631  static int vfio_iommu_type1_pin_pages(void *iommu_data,
95fc87b44104d9a Kirti Wankhede  2020-05-29  632  				      struct iommu_group *iommu_group,
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  633  				      unsigned long *user_pfn,
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  634  				      int npage, int prot,
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  635  				      unsigned long *phys_pfn)
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  636  {
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  637  	struct vfio_iommu *iommu = iommu_data;
95fc87b44104d9a Kirti Wankhede  2020-05-29  638  	struct vfio_group *group;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  639  	int i, j, ret;
2b172c0ea2a6daf Keqian Zhu      2020-12-10 @640  	unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
                                                                                      ^^^^^^^^^^^^^^^^^^^^
The patch introduces a new dereference.

a54eb55045ae9b3 Kirti Wankhede  2016-11-17  641  	unsigned long remote_vaddr;
2b172c0ea2a6daf Keqian Zhu      2020-12-10  642  	unsigned long bitmap_offset;
2b172c0ea2a6daf Keqian Zhu      2020-12-10  643  	unsigned long *bitmap_added;
2b172c0ea2a6daf Keqian Zhu      2020-12-10  644  	dma_addr_t iova;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  645  	struct vfio_dma *dma;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  646  	bool do_accounting;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  647  
a54eb55045ae9b3 Kirti Wankhede  2016-11-17 @648  	if (!iommu || !user_pfn || !phys_pfn)
                                                            ^^^^^^
Checked too late.

a54eb55045ae9b3 Kirti Wankhede  2016-11-17  649  		return -EINVAL;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  650  
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  651  	/* Supported for v2 version only */
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  652  	if (!iommu->v2)
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  653  		return -EACCES;
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  654  
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  655  	mutex_lock(&iommu->lock);
a54eb55045ae9b3 Kirti Wankhede  2016-11-17  656  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org 
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