[kbuild] drivers/soc/ti/k3-ringacc.c:562 k3_ringacc_ring_cfg() warn: variable dereferenced before check 'ring' (see line 559)

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   b791d1bdf9212d944d749a5c7ff6febdba241771
commit: 3277e8aa2504d97e022ecb9777d784ac1a439d36 soc: ti: k3: add navss ringacc driver
config: arm64-randconfig-m031-20200612 (attached as .config)
compiler: aarch64-linux-gcc (GCC) 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:
drivers/soc/ti/k3-ringacc.c:562 k3_ringacc_ring_cfg() warn: variable dereferenced before check 'ring' (see line 559)

# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3277e8aa2504d97e022ecb9777d784ac1a439d36
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git remote update linus
git checkout 3277e8aa2504d97e022ecb9777d784ac1a439d36
vim +/ring +562 drivers/soc/ti/k3-ringacc.c

3277e8aa2504d97 Grygorii Strashko 2020-01-15  557  int k3_ringacc_ring_cfg(struct k3_ring *ring, struct k3_ring_cfg *cfg)
3277e8aa2504d97 Grygorii Strashko 2020-01-15  558  {
3277e8aa2504d97 Grygorii Strashko 2020-01-15 @559  	struct k3_ringacc *ringacc = ring->parent;
                                                                                     ^^^^^^^^^^^^
Dereference.

3277e8aa2504d97 Grygorii Strashko 2020-01-15  560  	int ret = 0;
3277e8aa2504d97 Grygorii Strashko 2020-01-15  561  
3277e8aa2504d97 Grygorii Strashko 2020-01-15 @562  	if (!ring || !cfg)
                                                             ^^^^
Check too late.  Delete it?

3277e8aa2504d97 Grygorii Strashko 2020-01-15  563  		return -EINVAL;
3277e8aa2504d97 Grygorii Strashko 2020-01-15  564  	if (cfg->elm_size > K3_RINGACC_RING_ELSIZE_256 ||
3277e8aa2504d97 Grygorii Strashko 2020-01-15  565  	    cfg->mode >= K3_RINGACC_RING_MODE_INVALID ||
3277e8aa2504d97 Grygorii Strashko 2020-01-15  566  	    cfg->size & ~K3_RINGACC_CFG_RING_SIZE_ELCNT_MASK ||
3277e8aa2504d97 Grygorii Strashko 2020-01-15  567  	    !test_bit(ring->ring_id, ringacc->rings_inuse))
3277e8aa2504d97 Grygorii Strashko 2020-01-15  568  		return -EINVAL;
3277e8aa2504d97 Grygorii Strashko 2020-01-15  569  
3277e8aa2504d97 Grygorii Strashko 2020-01-15  570  	if (cfg->mode == K3_RINGACC_RING_MODE_MESSAGE &&

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