linux-kernel - [luxis1999-dev-iommu:iommufd-vfio-v5.16-rc1 21/32] drivers/iommufd/iommufd.c:163 iommufd_ioas_alloc() error: dereferencing freed memory 'ioas'

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Date:   Fri, 5 Nov 2021 12:39:47 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Liu Yi L <yi.l.liu@...el.com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [luxis1999-dev-iommu:iommufd-vfio-v5.16-rc1 21/32]
 drivers/iommufd/iommufd.c:163 iommufd_ioas_alloc() error: dereferencing
 freed memory 'ioas'

tree:   https://github.com/luxis1999/dev-iommu iommufd-vfio-v5.16-rc1
head:   0c6c7bdb5b3f7d4c8e6b03d34a59ac6bf3d02539
commit: a13cbd0a0fca96a74a170239e2e88e68940331c3 [21/32] iommufd: Add IOMMU_IOAS_ALLOC/FREE
config: x86_64-randconfig-m001-20211105 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

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

smatch warnings:
drivers/iommufd/iommufd.c:163 iommufd_ioas_alloc() error: dereferencing freed memory 'ioas'

vim +/ioas +163 drivers/iommufd/iommufd.c

a13cbd0a0fca96 Liu Yi L 2021-10-31  126  static int iommufd_ioas_alloc(struct iommufd_ctx *ictx, unsigned long arg)
a13cbd0a0fca96 Liu Yi L 2021-10-31  127  {
a13cbd0a0fca96 Liu Yi L 2021-10-31  128  	struct iommu_ioas_alloc req;
a13cbd0a0fca96 Liu Yi L 2021-10-31  129  	struct iommufd_ioas *ioas;
a13cbd0a0fca96 Liu Yi L 2021-10-31  130  	unsigned long minsz;
a13cbd0a0fca96 Liu Yi L 2021-10-31  131  	int ret;
a13cbd0a0fca96 Liu Yi L 2021-10-31  132  
a13cbd0a0fca96 Liu Yi L 2021-10-31  133  	minsz = offsetofend(struct iommu_ioas_alloc, addr_width);
a13cbd0a0fca96 Liu Yi L 2021-10-31  134  
a13cbd0a0fca96 Liu Yi L 2021-10-31  135  	if (copy_from_user(&req, (void __user *)arg, minsz))
a13cbd0a0fca96 Liu Yi L 2021-10-31  136  		return -EFAULT;
a13cbd0a0fca96 Liu Yi L 2021-10-31  137  
a13cbd0a0fca96 Liu Yi L 2021-10-31  138  	if (req.argsz < minsz || !req.addr_width ||
a13cbd0a0fca96 Liu Yi L 2021-10-31  139  	    req.flags != IOMMU_IOAS_ENFORCE_SNOOP ||
a13cbd0a0fca96 Liu Yi L 2021-10-31  140  	    req.type != IOMMU_IOAS_TYPE_KERNEL_TYPE1V2)
a13cbd0a0fca96 Liu Yi L 2021-10-31  141  		return -EINVAL;
a13cbd0a0fca96 Liu Yi L 2021-10-31  142  
a13cbd0a0fca96 Liu Yi L 2021-10-31  143  	ioas = kzalloc(sizeof(*ioas), GFP_KERNEL);
a13cbd0a0fca96 Liu Yi L 2021-10-31  144  	if (!ioas)
a13cbd0a0fca96 Liu Yi L 2021-10-31  145  		return -ENOMEM;
a13cbd0a0fca96 Liu Yi L 2021-10-31  146  
a13cbd0a0fca96 Liu Yi L 2021-10-31  147  	/* only supports kernel managed I/O page table so far */
a13cbd0a0fca96 Liu Yi L 2021-10-31  148  	ioas->type = IOMMU_IOAS_TYPE_KERNEL_TYPE1V2;
a13cbd0a0fca96 Liu Yi L 2021-10-31  149  	ioas->addr_width = req.addr_width;
a13cbd0a0fca96 Liu Yi L 2021-10-31  150  	/* only supports enforce snoop today */
a13cbd0a0fca96 Liu Yi L 2021-10-31  151  	ioas->enforce_snoop = true;
a13cbd0a0fca96 Liu Yi L 2021-10-31  152  	ioas->ictx = ictx;
a13cbd0a0fca96 Liu Yi L 2021-10-31  153  
a13cbd0a0fca96 Liu Yi L 2021-10-31  154  	refcount_set(&ioas->refs, 1);
a13cbd0a0fca96 Liu Yi L 2021-10-31  155  
a13cbd0a0fca96 Liu Yi L 2021-10-31  156  	ret = xa_alloc(&ictx->ioas_xa, &ioas->ioas_id, ioas,
a13cbd0a0fca96 Liu Yi L 2021-10-31  157  		       xa_limit_32b, GFP_KERNEL);
a13cbd0a0fca96 Liu Yi L 2021-10-31  158  	if (ret)
a13cbd0a0fca96 Liu Yi L 2021-10-31  159  		kfree(ioas);

Needs to return -ENOMEM here.

a13cbd0a0fca96 Liu Yi L 2021-10-31  160  
a13cbd0a0fca96 Liu Yi L 2021-10-31  161  	if (copy_to_user((void __user *)arg + minsz,
a13cbd0a0fca96 Liu Yi L 2021-10-31  162  			 &ioas->ioas_id, sizeof(ioas->ioas_id))) {
                                                                  ^^^^^^^^^^^^^
Already freed.

a13cbd0a0fca96 Liu Yi L 2021-10-31 @163  		xa_erase(&ictx->ioas_xa, ioas->ioas_id);
a13cbd0a0fca96 Liu Yi L 2021-10-31  164  		kfree(ioas);
a13cbd0a0fca96 Liu Yi L 2021-10-31  165  		ret = -EFAULT;
a13cbd0a0fca96 Liu Yi L 2021-10-31  166  	}
a13cbd0a0fca96 Liu Yi L 2021-10-31  167  
a13cbd0a0fca96 Liu Yi L 2021-10-31  168  	return ret;
a13cbd0a0fca96 Liu Yi L 2021-10-31  169  }

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