From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7D7636607F for ; Sun, 21 Jun 2026 14:47:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782053268; cv=none; b=bTCb4Cv24RXoFs7B/TflR/Jm1UIQmEs42yeg9ugH2B6h0lqX+B2zKTcpZy5AX+/Eu1d5lCJpif9vPlaJPA9P77T3LGR+zd3A99jnQk0wbjB7oJMLF5l5AVyLdIGmPyTzy8UtcPywGGgjL7a8M4Ixwvey8Z61tyre/fI1xb0QnPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782053268; c=relaxed/simple; bh=uGUH3MkZ3hacwEftYNi45APpHyxUseW+HS7LtmbqduI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=jRC3il3B5QfhVBLX2DQzt5Bdl2ew0PCIMfy5nokaGDqX4yg47B36GgBWFvsYRFRHZJBnCYF9Oylg5k9jCdcQD41h4EY9RMqqJzrpnC4gxdrBNKbxnZ5RFxcz518oP/QnQ3b9AKZCcuJBZOCFG13fThqLObOLuXtPA6YaojiJTpU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bctpm5Fl; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bctpm5Fl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D32F91F000E9; Sun, 21 Jun 2026 14:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782053267; bh=JPsVFaumn/9Au3VyylSVgcsQFOsrKEdbDU7Bc3IpKYY=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=bctpm5FleLoTdObfmUUM3f9NOfhyqSSOgAox5mnDzmrME9zcfvMRMTehn6NlxkOb/ h9MMZQwloH70vqH4nm8w0JpmgPOPrzoMqK0JW7+Ex/f2YdCo/5VzOln+qmIqFc58wH 6SdldTghKGWObzhcC7KOC8koxxuRT3BA8vY85nQtO0J9tysTE3pXely71LMwdeHbfM Mm/NVkUhkaZViMf8C8iY6OiwfVZ5cNOmlucjpn/s/DjqZJhq9XPSAVC+Ot35K2rVld iHw2qY+sozDiOeP6EYMHSRqqfX6dkpYuKhwdA0wfYEZLo6cXsla41tdHWw31IURjkg JvSH1BvaXWnUQ== From: Thomas Gleixner To: syzbot , anna-maria@linutronix.de, frederic@kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Cc: Surya Sai Madhu , Peter Zijlstra Subject: [PATCH] debugobjects: Plug race against a concurrent OOM disable In-Reply-To: <87y0g8nbe4.ffs@fw13> References: <6a2fac31.be3f099c.2836ae.0017.GAE@google.com> <87y0g8nbe4.ffs@fw13> Date: Sun, 21 Jun 2026 16:47:44 +0200 Message-ID: <874iiwlzlb.ffs@fw13> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain syzbot reported a puzzling splat: WARNING: kernel/time/hrtimer.c:443 at stub_timer+0xa/0x20 stub_timer() is installed as timer callback function in hrtimer_fixup_assert_init(), which is invoked when debug_object_assert_init() can't find a shadow object. In that case debug objects emits a warning about it before invoking the fixup. Though the provided console log lacks this warning and instead has the following a few seconds before the splat: ODEBUG: Out of memory. ODEBUG disabled So the object was looked up in debug_object_assert_init() and the lookup failed due a concurrent out of memory situation which disabled debug objects and freed the shadow objects: debug_object_assert_init() if (!debug_objects_enabled) return; obj = alloc(); if (!obj) { // Out of memory debug_objects_enabled = false; free_objects(); obj = lookup_or_alloc(); // The lookup failed because the other side // removed the objects, so this returns // an error code as the object in question // is not statically initialized if (!IS_ERR_OR_NULL(obj)) return; if (!obj) { debug_oom(); return; } print(...) if (!debug_objects_enabled) return; fixup(...) The debug object splat is skipped because debug_objects_enabled is false, but the fixup callback is invoked unconditionally, which makes the timer disfunctional. This is only a problem in debug_object_assert_init() and debug_object_activate() as both have to handle statically initialized objects and therefore must handle the error pointer return case gracefully. All other places only handle the found/not found case and the NULL pointer return is a signal for OOM. Otherwise they get a valid shadow object. Plug the hole by checking whether debug objects are still enabled before invoking the print and fixup function in those two places. Fixes: b84d435cc228 ("debugobjects: Extend to assert that an object is initialized") Reported-by: syzbot+5e8dda76ca21dae314b6@syzkaller.appspotmail.com Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org --- lib/debugobjects.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -894,6 +894,14 @@ int debug_object_activate(void *addr, co } raw_spin_unlock_irqrestore(&db->lock, flags); + + /* + * lookup_object_or_alloc() might have raced with a concurrent + * allocation failure which disabled debug objects. + */ + if (!debug_objects_enabled) + return 0; + debug_print_object(&o, "activate"); switch (o.state) { @@ -1071,6 +1079,15 @@ void debug_object_assert_init(void *addr return; } + /* + * lookup_object_or_alloc() might have raced with a concurrent + * allocation failure which disabled debug objects. Don't run the fixup + * as it might turn a valid object useless. See for example + * hrtimer_fixup_assert_init(). + */ + if (!debug_objects_enabled) + return; + /* Object is neither tracked nor static. It's not initialized. */ debug_print_object(&o, "assert_init"); debug_object_fixup(descr->fixup_assert_init, addr, ODEBUG_STATE_NOTAVAILABLE);