Re: [PATCH net 4/5] netdevsim: use IS_ERR instead of IS_ERR_OR_NULL for debugfs

[Dan Carpenter <dan.carpenter@oracle.com>]

Hi Taehee,

url:    https://github.com/0day-ci/linux/commits/Taehee-Yoo/netdevsim-fix-a-several-bugs-in-netdevsim-module/20200112-004546
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git a5c3a7c0ce1a1cfab15404018933775d7222a517

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

smatch warnings:
drivers/net/netdevsim/bpf.c:246 nsim_bpf_create_prog() error: dereferencing freed memory 'state'

# https://github.com/0day-ci/linux/commit/923e31529b0b3f039f837f54c4a1bbd77793256b
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 923e31529b0b3f039f837f54c4a1bbd77793256b
vim +/state +246 drivers/net/netdevsim/bpf.c

d514f41e793d2c Jiri Pirko     2019-04-25  227  static int nsim_bpf_create_prog(struct nsim_dev *nsim_dev,
b26b6946a62f37 Jiri Pirko     2019-04-12  228  				struct bpf_prog *prog)
31d3ad832948c7 Jakub Kicinski 2017-12-01  229  {
31d3ad832948c7 Jakub Kicinski 2017-12-01  230  	struct nsim_bpf_bound_prog *state;
31d3ad832948c7 Jakub Kicinski 2017-12-01  231  	char name[16];
31d3ad832948c7 Jakub Kicinski 2017-12-01  232  
31d3ad832948c7 Jakub Kicinski 2017-12-01  233  	state = kzalloc(sizeof(*state), GFP_KERNEL);
31d3ad832948c7 Jakub Kicinski 2017-12-01  234  	if (!state)
31d3ad832948c7 Jakub Kicinski 2017-12-01  235  		return -ENOMEM;
31d3ad832948c7 Jakub Kicinski 2017-12-01  236  
d514f41e793d2c Jiri Pirko     2019-04-25  237  	state->nsim_dev = nsim_dev;
31d3ad832948c7 Jakub Kicinski 2017-12-01  238  	state->prog = prog;
31d3ad832948c7 Jakub Kicinski 2017-12-01  239  	state->state = "verify";
31d3ad832948c7 Jakub Kicinski 2017-12-01  240  
31d3ad832948c7 Jakub Kicinski 2017-12-01  241  	/* Program id is not populated yet when we create the state. */
d514f41e793d2c Jiri Pirko     2019-04-25  242  	sprintf(name, "%u", nsim_dev->prog_id_gen++);
d514f41e793d2c Jiri Pirko     2019-04-25  243  	state->ddir = debugfs_create_dir(name, nsim_dev->ddir_bpf_bound_progs);
923e31529b0b3f Taehee Yoo     2020-01-11  244  	if (IS_ERR(state->ddir)) {
31d3ad832948c7 Jakub Kicinski 2017-12-01  245  		kfree(state);
                                                              ^^^^^
state is freed.

923e31529b0b3f Taehee Yoo     2020-01-11 @246  		return PTR_ERR(state->ddir);
                                                                       ^^^^^^^^^^^
Then dereferenced afterward.

31d3ad832948c7 Jakub Kicinski 2017-12-01  247  	}
31d3ad832948c7 Jakub Kicinski 2017-12-01  248  
31d3ad832948c7 Jakub Kicinski 2017-12-01  249  	debugfs_create_u32("id", 0400, state->ddir, &prog->aux->id);
31d3ad832948c7 Jakub Kicinski 2017-12-01  250  	debugfs_create_file("state", 0400, state->ddir,
31d3ad832948c7 Jakub Kicinski 2017-12-01  251  			    &state->state, &nsim_bpf_string_fops);
31d3ad832948c7 Jakub Kicinski 2017-12-01  252  	debugfs_create_bool("loaded", 0400, state->ddir, &state->is_loaded);
31d3ad832948c7 Jakub Kicinski 2017-12-01  253  
d514f41e793d2c Jiri Pirko     2019-04-25  254  	list_add_tail(&state->l, &nsim_dev->bpf_bound_progs);
31d3ad832948c7 Jakub Kicinski 2017-12-01  255  
31d3ad832948c7 Jakub Kicinski 2017-12-01  256  	prog->aux->offload->dev_priv = state;
31d3ad832948c7 Jakub Kicinski 2017-12-01  257  
31d3ad832948c7 Jakub Kicinski 2017-12-01  258  	return 0;
31d3ad832948c7 Jakub Kicinski 2017-12-01  259  }

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