From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 699392EE16D; Mon, 5 May 2025 23:09:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486545; cv=none; b=niDhWJiQV9H4+wu98IOzGe52rSZk9bDEDiQZHljblPD3hHX3AQ1hbe5UFjnSuAmQV1HVMbYPERFVxTy4FeAroKc6NplNRZFdrCzi2EAS8zcllcNwprVJ+ESEryz21MMSfM0WD/fOsefxJiO4IxrNbQLo9SccHfot/M58mCstD2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486545; c=relaxed/simple; bh=SRnRJO6g1B7jvzWhfxhh5YTRN7XIca6siImFMw6aC7c=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Z19XXIO6QvSqojVe77R77LeQQEzON0ry7UgwmWv2H/dJLy2ajpKi2f0Hfj+mlYIjSoS0MzJN/kCpzHZlQJtN4wOdfcmFnimyVA2VGLGclkWnIkSe8/xi/z3RlW//JHH2EWzGg2K0PgfCd74ydiHVru7r0eBxKj/I+tUOqzeDy4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RAK9SlgA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RAK9SlgA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4843DC4CEE4; Mon, 5 May 2025 23:09:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746486545; bh=SRnRJO6g1B7jvzWhfxhh5YTRN7XIca6siImFMw6aC7c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RAK9SlgAyY63JbqUCLnAH7K3yy5WmOAbkhSwB4Q3PQZdb5NcZGqHz7qkU0kPlo0jQ 19I6BSVBNcr8uoi/3geh7VZYWIQM4gdo2VvGBW4Nc0b8VOclUmYiqZjpYoVkxSMKVt gZ5/BkgYGUkfcsubVtoyRFwoJMYUFBVf+cbCGbXVq/AC+gBy4Og5rCERzRg2FR5bpj K6hlSErCkjIHe+bak5JwelRqTSH+ABtE9rkdaQ0O3vJR+XkesAX5wYnCNXgKciMhE6 scdC8RqixEzCoIABN5zE2gAEaCDLPQ92IkBzVn3Xh6wMOTjlCIMwsvPYbgJ3QbDKy6 b68fX+BcBUhFg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Takashi Iwai , syzbot+2d373c9936c00d7e120c@syzkaller.appspotmail.com, Sasha Levin , perex@perex.cz, tiwai@suse.com, viro@zeniv.linux.org.uk, linux-sound@vger.kernel.org Subject: [PATCH AUTOSEL 6.1 082/212] ALSA: seq: Improve data consistency at polling Date: Mon, 5 May 2025 19:04:14 -0400 Message-Id: <20250505230624.2692522-82-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250505230624.2692522-1-sashal@kernel.org> References: <20250505230624.2692522-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.136 Content-Transfer-Encoding: 8bit From: Takashi Iwai [ Upstream commit e3cd33ab17c33bd8f1a9df66ec83a15dd8f7afbb ] snd_seq_poll() calls snd_seq_write_pool_allocated() that reads out a field in client->pool object, while it can be updated concurrently via ioctls, as reported by syzbot. The data race itself is harmless, as it's merely a poll() call, and the state is volatile. OTOH, the read out of poll object info from the caller side is fragile, and we can leave it better in snd_seq_pool_poll_wait() alone. A similar pattern is seen in snd_seq_kernel_client_write_poll(), too, which is called from the OSS sequencer. This patch drops the pool checks from the caller side and add the pool->lock in snd_seq_pool_poll_wait() for better data consistency. Reported-by: syzbot+2d373c9936c00d7e120c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/67c88903.050a0220.15b4b9.0028.GAE@google.com Link: https://patch.msgid.link/20250307084246.29271-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/seq/seq_clientmgr.c | 5 +---- sound/core/seq/seq_memory.c | 1 + 2 files changed, 2 insertions(+), 4 deletions(-) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 2d707afa1ef1c..1252ea7ad55ea 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1140,8 +1140,7 @@ static __poll_t snd_seq_poll(struct file *file, poll_table * wait) if (snd_seq_file_flags(file) & SNDRV_SEQ_LFLG_OUTPUT) { /* check if data is available in the pool */ - if (!snd_seq_write_pool_allocated(client) || - snd_seq_pool_poll_wait(client->pool, file, wait)) + if (snd_seq_pool_poll_wait(client->pool, file, wait)) mask |= EPOLLOUT | EPOLLWRNORM; } @@ -2382,8 +2381,6 @@ int snd_seq_kernel_client_write_poll(int clientid, struct file *file, poll_table if (client == NULL) return -ENXIO; - if (! snd_seq_write_pool_allocated(client)) - return 1; if (snd_seq_pool_poll_wait(client->pool, file, wait)) return 1; return 0; diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c index 47ef6bc30c0ee..e30b92d85079b 100644 --- a/sound/core/seq/seq_memory.c +++ b/sound/core/seq/seq_memory.c @@ -366,6 +366,7 @@ int snd_seq_pool_poll_wait(struct snd_seq_pool *pool, struct file *file, poll_table *wait) { poll_wait(file, &pool->output_sleep, wait); + guard(spinlock_irq)(&pool->lock); return snd_seq_output_ok(pool); } -- 2.39.5