From patchwork Mon May 18 17:37:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 225660 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D326C433E0 for ; Mon, 18 May 2020 18:16:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7289A20671 for ; Mon, 18 May 2020 18:16:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589825803; bh=V1Ja0lg4oMTIl71tYsWdRm+4wxF6tLKWIy2gbpYiJMU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=nzZ5IX8+z4GHT3d73Pgb+k4w+n8S4LtiqVGya8klQRKx91TOh14PhakfL+l64XEA7 0MIqAmRV9Lb1YVBRDz5zKDISE5QxUUzH42l/AArEz0wbL3iOmUpM5o0kB0xKWTj9BU rin2dIFuVXdlZB1nVzPPXWa+oKdVQjtIVwyyctss= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731850AbgERR6B (ORCPT ); Mon, 18 May 2020 13:58:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:37008 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731847AbgERR6A (ORCPT ); Mon, 18 May 2020 13:58:00 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 52D2A20715; Mon, 18 May 2020 17:57:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824679; bh=V1Ja0lg4oMTIl71tYsWdRm+4wxF6tLKWIy2gbpYiJMU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MEcPpG/p40yL0xI0pnWgU2j6q+XlDrrluzImHhLCVeA9j+TFMr5o10LZuGImKefcU nfoE2DQXTq/AGuI9o1t4tCUSQ/EAuPn6kg7OrKzquhjLgMn7KpPJyfxJC/OVy05NFN wpSlthcdGb5xPyREBTkLUifCanjs3CxsAtRSoi88= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, butt3rflyh4ck , Takashi Iwai Subject: [PATCH 5.4 107/147] ALSA: rawmidi: Fix racy buffer resize under concurrent accesses Date: Mon, 18 May 2020 19:37:10 +0200 Message-Id: <20200518173526.564944717@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200518173513.009514388@linuxfoundation.org> References: <20200518173513.009514388@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Takashi Iwai commit c1f6e3c818dd734c30f6a7eeebf232ba2cf3181d upstream. The rawmidi core allows user to resize the runtime buffer via ioctl, and this may lead to UAF when performed during concurrent reads or writes: the read/write functions unlock the runtime lock temporarily during copying form/to user-space, and that's the race window. This patch fixes the hole by introducing a reference counter for the runtime buffer read/write access and returns -EBUSY error when the resize is performed concurrently against read/write. Note that the ref count field is a simple integer instead of refcount_t here, since the all contexts accessing the buffer is basically protected with a spinlock, hence we need no expensive atomic ops. Also, note that this busy check is needed only against read / write functions, and not in receive/transmit callbacks; the race can happen only at the spinlock hole mentioned in the above, while the whole function is protected for receive / transmit callbacks. Reported-by: butt3rflyh4ck Cc: Link: https://lore.kernel.org/r/CAFcO6XMWpUVK_yzzCpp8_XP7+=oUpQvuBeCbMffEDkpe8jWrfg@mail.gmail.com Link: https://lore.kernel.org/r/s5heerw3r5z.wl-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- include/sound/rawmidi.h | 1 + sound/core/rawmidi.c | 31 +++++++++++++++++++++++++++---- 2 files changed, 28 insertions(+), 4 deletions(-) --- a/include/sound/rawmidi.h +++ b/include/sound/rawmidi.h @@ -61,6 +61,7 @@ struct snd_rawmidi_runtime { size_t avail_min; /* min avail for wakeup */ size_t avail; /* max used buffer for wakeup */ size_t xruns; /* over/underruns counter */ + int buffer_ref; /* buffer reference count */ /* misc */ spinlock_t lock; wait_queue_head_t sleep; --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -97,6 +97,17 @@ static void snd_rawmidi_input_event_work runtime->event(runtime->substream); } +/* buffer refcount management: call with runtime->lock held */ +static inline void snd_rawmidi_buffer_ref(struct snd_rawmidi_runtime *runtime) +{ + runtime->buffer_ref++; +} + +static inline void snd_rawmidi_buffer_unref(struct snd_rawmidi_runtime *runtime) +{ + runtime->buffer_ref--; +} + static int snd_rawmidi_runtime_create(struct snd_rawmidi_substream *substream) { struct snd_rawmidi_runtime *runtime; @@ -646,6 +657,11 @@ static int resize_runtime_buffer(struct if (!newbuf) return -ENOMEM; spin_lock_irq(&runtime->lock); + if (runtime->buffer_ref) { + spin_unlock_irq(&runtime->lock); + kvfree(newbuf); + return -EBUSY; + } oldbuf = runtime->buffer; runtime->buffer = newbuf; runtime->buffer_size = params->buffer_size; @@ -945,8 +961,10 @@ static long snd_rawmidi_kernel_read1(str long result = 0, count1; struct snd_rawmidi_runtime *runtime = substream->runtime; unsigned long appl_ptr; + int err = 0; spin_lock_irqsave(&runtime->lock, flags); + snd_rawmidi_buffer_ref(runtime); while (count > 0 && runtime->avail) { count1 = runtime->buffer_size - runtime->appl_ptr; if (count1 > count) @@ -965,16 +983,19 @@ static long snd_rawmidi_kernel_read1(str if (userbuf) { spin_unlock_irqrestore(&runtime->lock, flags); if (copy_to_user(userbuf + result, - runtime->buffer + appl_ptr, count1)) { - return result > 0 ? result : -EFAULT; - } + runtime->buffer + appl_ptr, count1)) + err = -EFAULT; spin_lock_irqsave(&runtime->lock, flags); + if (err) + goto out; } result += count1; count -= count1; } + out: + snd_rawmidi_buffer_unref(runtime); spin_unlock_irqrestore(&runtime->lock, flags); - return result; + return result > 0 ? result : err; } long snd_rawmidi_kernel_read(struct snd_rawmidi_substream *substream, @@ -1268,6 +1289,7 @@ static long snd_rawmidi_kernel_write1(st return -EAGAIN; } } + snd_rawmidi_buffer_ref(runtime); while (count > 0 && runtime->avail > 0) { count1 = runtime->buffer_size - runtime->appl_ptr; if (count1 > count) @@ -1299,6 +1321,7 @@ static long snd_rawmidi_kernel_write1(st } __end: count1 = runtime->avail < runtime->buffer_size; + snd_rawmidi_buffer_unref(runtime); spin_unlock_irqrestore(&runtime->lock, flags); if (count1) snd_rawmidi_output_trigger(substream, 1);