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 75339C43334 for ; Tue, 14 Jun 2022 11:46:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241029AbiFNLqV (ORCPT ); Tue, 14 Jun 2022 07:46:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231256AbiFNLqT (ORCPT ); Tue, 14 Jun 2022 07:46:19 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9EA0F47063 for ; Tue, 14 Jun 2022 04:46:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id D43E01F8F1; Tue, 14 Jun 2022 11:46:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1655207175; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5MBwxAfQXFMwK4dY1FSCu0teVo0QJweWujfRkKyJQKA=; b=Wy00PtzHHpEfNjMq68sFxjBUQWRtyawvl6foxApnNBq4tymk9TxmvwRso7OYky8553EoxQ g3Ido1+BdLoZT8O4IZ6V4vR3KGYvZfgRQPezubHVDiveyJc/brwpJXsicF59m+oLbCGBxK iVqBHjryRIyuIrIk2UKpWRxb4vJdbrc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1655207175; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5MBwxAfQXFMwK4dY1FSCu0teVo0QJweWujfRkKyJQKA=; b=H2W3S1kZKE1KSUWxueluPIG3aYUXqlzNwt5nXDf/j+lFjxlYZmij0SY1PGqh5Jr8iORK5k OLWJkiBkloJoXPDQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id AD7B1139EC; Tue, 14 Jun 2022 11:46:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id TUjKKQd1qGI1eQAAMHmgww (envelope-from ); Tue, 14 Jun 2022 11:46:15 +0000 Date: Tue, 14 Jun 2022 13:46:15 +0200 Message-ID: <87v8t3piwo.wl-tiwai@suse.de> From: Takashi Iwai To: "Fabio M. De Francesco" Cc: Eugeniu Rosca , Jaroslav Kysela , Takashi Iwai , Mark Brown , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, syzbot+205eb15961852c2c5974@syzkaller.appspotmail.com, naveenkumar.sunkari@in.bosch.com, Eugeniu Rosca Subject: Re: [PATCH] ALSA: pcm: Test for "silence" field in struct "pcm_format_data" In-Reply-To: <8079585.T7Z3S40VBb@opensuse> References: <20220409012655.9399-1-fmdefrancesco@gmail.com> <2245197.ElGaqSPkdT@opensuse> <87y1xzplj1.wl-tiwai@suse.de> <8079585.T7Z3S40VBb@opensuse> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 14 Jun 2022 13:30:13 +0200, Fabio M. De Francesco wrote: > > On marted́ 14 giugno 2022 12:49:38 CEST Takashi Iwai wrote: > > On Tue, 14 Jun 2022 12:43:16 +0200, > > Fabio M. De Francesco wrote: > > > > > > On marted́ 14 giugno 2022 11:58:51 CEST Eugeniu Rosca wrote: > > > > Hello Fabio, hello All, > > > > > > > > On Sa, Apr 09, 2022 at 03:26:55 +0200, Fabio M. De Francesco wrote: > > > > > Syzbot reports "KASAN: null-ptr-deref Write in > > > > > snd_pcm_format_set_silence".[1] > > > > > > > > > > It is due to missing validation of the "silence" field of struct > > > > > "pcm_format_data" in "pcm_formats" array. > > > > > > > > > > Add a test for valid "pat" and, if it is not so, return -EINVAL. > > > > > > > > > > [1] https://lore.kernel.org/lkml/ > > > 000000000000d188ef05dc2c7279@google.com/ > > > > > > > > > > Reported-and-tested-by: > > > syzbot+205eb15961852c2c5974@syzkaller.appspotmail.com > > > > > Signed-off-by: Fabio M. De Francesco > > > > > --- > > > > > > > > > > I wasn't able to figure out the commit for the "Fixes:" tag. If > this > > > patch > > > > > is good, can someone please help with providing this missing > > > information? > > > > > > > > > > sound/core/pcm_misc.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c > > > > > index 4866aed97aac..5588b6a1ee8b 100644 > > > > > --- a/sound/core/pcm_misc.c > > > > > +++ b/sound/core/pcm_misc.c > > > > > @@ -433,7 +433,7 @@ int snd_pcm_format_set_silence(snd_pcm_format_t > > > format, void *data, unsigned int > > > > > return 0; > > > > > width = pcm_formats[(INT)format].phys; /* physical width */ > > > > > pat = pcm_formats[(INT)format].silence; > > > > > - if (! width) > > > > > + if (!width || !pat) > > > > > return -EINVAL; > > > > > /* signed or 1 byte data */ > > > > > if (pcm_formats[(INT)format].signd == 1 || width <= 8) { > > > > > > > > JFYI, PVS-Studio 7.19 reports: > > > > > > > > sound/core/pcm_misc.c 409 warn V560 A part of > > > conditional expression is always false: !pat. > > > > > > Sorry, I assumed (wrongly!) that when we have > > > > > > static const struct pcm_format_data > > > pcm_formats[(INT)SNDRV_PCM_FORMAT_LAST+1] = { > > > [SNDRV_PCM_FORMAT_S8] = { > > > .width = 8, .phys = 8, .le = -1, .signd = 1, > > > .silence = {}, > > > }, > > > [snip] > > > /* FIXME: the following two formats are not defined properly yet > > > */ > > > [SNDRV_PCM_FORMAT_MPEG] = { > > > .le = -1, .signd = -1, > > > }, > > > [SNDRV_PCM_FORMAT_GSM] = { > > > .le = -1, .signd = -1, > > > }, > > > > > > pointer "silence", and then "pat", must be NULL. > > > > Oh right, those are missing ones. I haven't realized that those > > formats are allowed by PCM OSS layer. > > > > Practically seen, those formats have never been used in reality, and > > we may consider dropping them completely to plug such holes... > > > Does it imply that my argument is correct or my "fix" can't yet catch those > missing ones? Your fix should catch the case with a NULL pat pointer, I guess. PCM OSS layer allows this format, so this could be hit. However, whether it's really a fix for the given syzkaller code path, it's doubtful. Nevertheless, your check is still worth to keep. > Besides the question above, I want to notice that we have one more /* FIXME > */ entry... > > /* FIXME: the following format is not defined properly yet */ > [SNDRV_PCM_FORMAT_SPECIAL] = { > .le = -1, .signd = -1, > }, > > If you want I can get rid of those three entries if you confirm they can > safely be deleted. In a second patch I can also remove that unnecessary > check for valid "pat". Well, you can't "delete" those entries so easiy. The formats themselves are still allowed for user-space, hence every caller needs to check. If any, we need to add the check in valid_format() for such unsupported formats, then drop the rest checks and entries. thanks, Takashi