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Subject[axboe-block:for-5.17/block 106/108] block/blk-ioc.c:307 set_task_ioprio() error: we previously assumed 'task->io_context' could be null (see line 300)
tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-5.17/block
head: 5ef1630586317e92c9ebd7b4ce48f393b7ff790f
commit: 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7 [106/108] block: open code create_task_io_context in set_task_ioprio
config: i386-randconfig-m021-20211216 (https://download.01.org/0day-ci/archive/20211217/202112171520.5hNnOM0q-lkp@intel.com/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@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
block/blk-ioc.c:307 set_task_ioprio() error: we previously assumed 'task->io_context' could be null (see line 300)

vim +307 block/blk-ioc.c

a411cd3cfdc5bb Christoph Hellwig 2021-12-09 271 int set_task_ioprio(struct task_struct *task, int ioprio)
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 272 {
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 273 int err;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 274 const struct cred *cred = current_cred(), *tcred;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 275
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 276 rcu_read_lock();
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 277 tcred = __task_cred(task);
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 278 if (!uid_eq(tcred->uid, cred->euid) &&
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 279 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 280 rcu_read_unlock();
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 281 return -EPERM;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 282 }
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 283 rcu_read_unlock();
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 284
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 285 err = security_task_setioprio(task, ioprio);
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 286 if (err)
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 287 return err;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 288
8472161b77c41d Christoph Hellwig 2021-12-09 289 task_lock(task);
8472161b77c41d Christoph Hellwig 2021-12-09 290 if (unlikely(!task->io_context)) {
8472161b77c41d Christoph Hellwig 2021-12-09 291 struct io_context *ioc;
8472161b77c41d Christoph Hellwig 2021-12-09 292
8472161b77c41d Christoph Hellwig 2021-12-09 293 task_unlock(task);
5fc11eebb4a98d Christoph Hellwig 2021-12-09 294
5fc11eebb4a98d Christoph Hellwig 2021-12-09 295 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
5fc11eebb4a98d Christoph Hellwig 2021-12-09 296 if (!ioc)
5fc11eebb4a98d Christoph Hellwig 2021-12-09 297 return -ENOMEM;
5fc11eebb4a98d Christoph Hellwig 2021-12-09 298
5fc11eebb4a98d Christoph Hellwig 2021-12-09 299 task_lock(task);
5fc11eebb4a98d Christoph Hellwig 2021-12-09 @300 if (task->io_context || (task->flags & PF_EXITING)) {
^^^^^^^^^^^^^^^^^^^^^^^^
Assume "task->io_context" is NULL but PF_EXITING is set.

5fc11eebb4a98d Christoph Hellwig 2021-12-09 301 kmem_cache_free(iocontext_cachep, ioc);
5fc11eebb4a98d Christoph Hellwig 2021-12-09 302 ioc = task->io_context;
5fc11eebb4a98d Christoph Hellwig 2021-12-09 303 } else {
5fc11eebb4a98d Christoph Hellwig 2021-12-09 304 task->io_context = ioc;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 305 }
8472161b77c41d Christoph Hellwig 2021-12-09 306 }
8472161b77c41d Christoph Hellwig 2021-12-09 @307 task->io_context->ioprio = ioprio;
^^^^^^^^^^^^^^^^^^
Unchecked dereference.

8472161b77c41d Christoph Hellwig 2021-12-09 308 task_unlock(task);
8472161b77c41d Christoph Hellwig 2021-12-09 309 return 0;
a411cd3cfdc5bb Christoph Hellwig 2021-12-09 310 }

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

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