Re: [PATCHv2 1/4] block: bio-integrity: directly map user buffers

[kernel test robot <lkp@intel.com>]

Hi Keith,

kernel test robot noticed the following build warnings:

[auto build test WARNING on axboe-block/for-next]
[also build test WARNING on linus/master v6.6 next-20231030]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Keith-Busch/block-bio-integrity-directly-map-user-buffers/20231028-022107
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
patch link:    https://lore.kernel.org/r/20231027181929.2589937-2-kbusch%40meta.com
patch subject: [PATCHv2 1/4] block: bio-integrity: directly map user buffers
config: x86_64-rhel-8.3-rust (https://download.01.org/0day-ci/archive/20231031/202310310704.l4FwoJDd-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231031/202310310704.l4FwoJDd-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310310704.l4FwoJDd-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> block/bio-integrity.c:215:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (!buf)
               ^~~~
   block/bio-integrity.c:255:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   block/bio-integrity.c:215:2: note: remove the 'if' if its condition is always false
           if (!buf)
           ^~~~~~~~~
   block/bio-integrity.c:204:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   1 warning generated.


vim +215 block/bio-integrity.c

   195	
   196	static int bio_integrity_copy_user(struct bio *bio, struct bio_vec *bvec,
   197					   int nr_vecs, unsigned int len,
   198					   unsigned int direction, u32 seed)
   199	{
   200		struct bio_integrity_payload *bip;
   201		struct bio_vec *copy_vec = NULL;
   202		struct iov_iter iter;
   203		void *buf;
   204		int ret;
   205	
   206		/* if bvec is on the stack, we need to allocate a copy for the completion */
   207		if (nr_vecs <= UIO_FASTIOV) {
   208			copy_vec = kcalloc(sizeof(*bvec), nr_vecs, GFP_KERNEL);
   209			if (!copy_vec)
   210				return -ENOMEM;
   211			memcpy(copy_vec, bvec, nr_vecs * sizeof(*bvec));
   212		}
   213	
   214		buf = kmalloc(len, GFP_KERNEL);
 > 215		if (!buf)
   216			goto free_copy;
   217	
   218		if (direction == ITER_SOURCE) {
   219			iov_iter_bvec(&iter, direction, bvec, nr_vecs, len);
   220			if (!copy_from_iter_full(buf, len, &iter)) {
   221				ret = -EFAULT;
   222				goto free_buf;
   223			}
   224		} else {
   225			memset(buf, 0, len);
   226		}
   227	
   228		/*
   229		 * We just need one vec for this bip, but we need to preserve the
   230		 * number of vecs in the user bvec for the completion handling, so use
   231		 * nr_vecs.
   232		 */
   233		bip = bio_integrity_alloc(bio, GFP_KERNEL, nr_vecs);
   234		if (IS_ERR(bip)) {
   235			ret = PTR_ERR(bip);
   236			goto free_buf;
   237		}
   238	
   239		ret = bio_integrity_add_page(bio, virt_to_page(buf), len,
   240					     offset_in_page(buf));
   241		if (ret != len) {
   242			ret = -ENOMEM;
   243			goto free_bip;
   244		}
   245	
   246		bip->bip_flags |= BIP_INTEGRITY_USER;
   247		bip->copy_vec = copy_vec ?: bvec;
   248		return 0;
   249	free_bip:
   250		bio_integrity_free(bio);
   251	free_buf:
   252		kfree(buf);
   253	free_copy:
   254		kfree(copy_vec);
   255		return ret;
   256	}
   257	

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