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debugobjects: Recheck debug_objects_enabled before reporting

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syzbot is reporting false a positive ODEBUG message immediately after
ODEBUG was disabled due to OOM.

  [ 1062.309646][T22911] ODEBUG: Out of memory. ODEBUG disabled
  [ 1062.886755][ T5171] ------------[ cut here ]------------
  [ 1062.892770][ T5171] ODEBUG: assert_init not available (active state 0) object: ffffc900056afb20 object type: timer_list hint: process_timeout+0x0/0x40

  CPU 0 [ T5171]                CPU 1 [T22911]
  --------------                --------------
  debug_object_assert_init() {
    if (!debug_objects_enabled)
      return;
    db = get_bucket(addr);
                                lookup_object_or_alloc() {
                                  debug_objects_enabled = 0;
                                  return NULL;
                                }
                                debug_objects_oom() {
                                  pr_warn("Out of memory. ODEBUG disabled\n");
                                  // all buckets get emptied here, and
                                }
    lookup_object_or_alloc(addr, db, descr, false, true) {
      // this bucket is already empty.
      return ERR_PTR(-ENOENT);
    }
    // Emits false positive warning.
    debug_print_object(&o, "assert_init");
  }

Recheck debug_object_enabled in debug_print_object() to avoid that.

Reported-by: syzbot <syzbot+7937ba6a50bdd00fffdf@syzkaller.appspotmail.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/492fe2ae-5141-d548-ebd5-62f5fe2e57f7@I-love.SAKURA.ne.jp
Closes: https://syzkaller.appspot.com/bug?extid=7937ba6a50bdd00fffdf
This commit is contained in:
Tetsuo Handa 2023-06-07 19:19:02 +09:00 committed by Thomas Gleixner
parent 7877cb91f1
commit 8b64d420fe
1 changed files with 9 additions and 0 deletions
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9
lib/debugobjects.c
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@ -498,6 +498,15 @@ static void debug_print_object(struct debug_obj *obj, char *msg)
const struct debug_obj_descr *descr = obj->descr;
static int limit;
/*
* Don't report if lookup_object_or_alloc() by the current thread
* failed because lookup_object_or_alloc()/debug_objects_oom() by a
* concurrent thread turned off debug_objects_enabled and cleared
* the hash buckets.
*/
if (!debug_objects_enabled)
return;
if (limit < 5 && descr != descr_test) {
void *hint = descr->debug_hint ?
descr->debug_hint(obj->object) : NULL;