From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 715BCC4332F for ; Wed, 2 Nov 2022 03:21:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230187AbiKBDVK (ORCPT ); Tue, 1 Nov 2022 23:21:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230115AbiKBDVI (ORCPT ); Tue, 1 Nov 2022 23:21:08 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A4E823383 for ; Tue, 1 Nov 2022 20:21:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C693DB8206F for ; Wed, 2 Nov 2022 03:21:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FA20C433C1; Wed, 2 Nov 2022 03:21:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667359265; bh=x9r6tYA3+3uSr9xQoaPHfp9Oc8suWSMO/Xz7qB+H8jQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=po0bj0LLGxU+zXNxSdfRkMkan8EKOCfu5NgtRi18qwhVUCf3aI+qd2NGhwcH3PsML ZgjsIA8E1VphhZ86/z+fou5xA++RHiwsBY86SiZwIdjuVY2mJ0LuG612Yn7q2lyMme DnkDsHQBNAgn4m4UdDlK5hSljACP3GjgBna8zrSc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Steven Rostedt (Google)" , Guenter Roeck , Takashi Iwai Subject: [PATCH 5.4 03/64] ALSA: Use del_timer_sync() before freeing timer Date: Wed, 2 Nov 2022 03:33:29 +0100 Message-Id: <20221102022051.933376166@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221102022051.821538553@linuxfoundation.org> References: <20221102022051.821538553@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Steven Rostedt (Google) commit f0a868788fcbf63cdab51f5adcf73b271ede8164 upstream. The current code for freeing the emux timer is extremely dangerous: CPU0 CPU1 ---- ---- snd_emux_timer_callback() snd_emux_free() spin_lock(&emu->voice_lock) del_timer(&emu->tlist); <-- returns immediately spin_unlock(&emu->voice_lock); [..] kfree(emu); spin_lock(&emu->voice_lock); [BOOM!] Instead just use del_timer_sync() which will wait for the timer to finish before continuing. No need to check if the timer is active or not when doing so. This doesn't fix the race of a possible re-arming of the timer, but at least it won't use the data that has just been freed. [ Fixed unused variable warning by tiwai ] Cc: stable@vger.kernel.org Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Steven Rostedt (Google) Reviewed-by: Guenter Roeck Link: https://lore.kernel.org/r/20221026231236.6834b551@gandalf.local.home Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/synth/emux/emux.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) --- a/sound/synth/emux/emux.c +++ b/sound/synth/emux/emux.c @@ -125,15 +125,10 @@ EXPORT_SYMBOL(snd_emux_register); */ int snd_emux_free(struct snd_emux *emu) { - unsigned long flags; - if (! emu) return -EINVAL; - spin_lock_irqsave(&emu->voice_lock, flags); - if (emu->timer_active) - del_timer(&emu->tlist); - spin_unlock_irqrestore(&emu->voice_lock, flags); + del_timer_sync(&emu->tlist); snd_emux_proc_free(emu); snd_emux_delete_virmidi(emu);