kernel/bpf/helpers.c:1260:33-38: ERROR: t is NULL but dereferenced.

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

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
CC: linux-kernel@vger.kernel.org
TO: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   bcc8eda6d34934d80b96adb8dc4ff5dfc632a53a
commit: b00628b1c7d595ae5b544e059c27b1f5828314b4 bpf: Introduce bpf timers.
date:   3 years, 5 months ago
:::::: branch date: 7 hours ago
:::::: commit date: 3 years, 5 months ago
config: x86_64-randconfig-102-20241120 (https://download.01.org/0day-ci/archive/20241201/202412011718.lsm0y2Aw-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

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>
| Reported-by: Julia Lawall <julia.lawall@inria.fr>
| Closes: https://lore.kernel.org/r/202412011718.lsm0y2Aw-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> kernel/bpf/helpers.c:1260:33-38: ERROR: t is NULL but dereferenced.

vim +1260 kernel/bpf/helpers.c

b00628b1c7d595 Alexei Starovoitov 2021-07-14  1232  
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1233  BPF_CALL_1(bpf_timer_cancel, struct bpf_timer_kern *, timer)
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1234  {
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1235  	struct bpf_hrtimer *t;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1236  	int ret = 0;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1237  
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1238  	if (in_nmi())
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1239  		return -EOPNOTSUPP;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1240  	__bpf_spin_lock_irqsave(&timer->lock);
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1241  	t = timer->timer;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1242  	if (!t) {
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1243  		ret = -EINVAL;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1244  		goto out;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1245  	}
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1246  	if (this_cpu_read(hrtimer_running) == t) {
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1247  		/* If bpf callback_fn is trying to bpf_timer_cancel()
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1248  		 * its own timer the hrtimer_cancel() will deadlock
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1249  		 * since it waits for callback_fn to finish
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1250  		 */
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1251  		ret = -EDEADLK;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1252  		goto out;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1253  	}
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1254  	drop_prog_refcnt(t);
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1255  out:
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1256  	__bpf_spin_unlock_irqrestore(&timer->lock);
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1257  	/* Cancel the timer and wait for associated callback to finish
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1258  	 * if it was running.
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1259  	 */
b00628b1c7d595 Alexei Starovoitov 2021-07-14 @1260  	ret = ret ?: hrtimer_cancel(&t->timer);
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1261  	return ret;
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1262  }
b00628b1c7d595 Alexei Starovoitov 2021-07-14  1263  

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