From 203d58930d4ac3287fe8a3c7e7be8b86a4dc20de Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 7 Jun 2023 19:19:02 +0900 Subject: [PATCH] debugobjects: Recheck debug_objects_enabled before reporting commit 8b64d420fe2450f82848178506d3e3a0bd195539 upstream. 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 Suggested-by: Thomas Gleixner Signed-off-by: Tetsuo Handa Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/492fe2ae-5141-d548-ebd5-62f5fe2e57f7@I-love.SAKURA.ne.jp Closes: https://syzkaller.appspot.com/bug?extid=7937ba6a50bdd00fffdf Signed-off-by: Greg Kroah-Hartman --- lib/debugobjects.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/lib/debugobjects.c b/lib/debugobjects.c index c46736210363..dacb80c22c4f 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -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;