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 E36562EEBFB; Mon, 5 May 2025 22:23:27 +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=1746483808; cv=none; b=UTpD7geIqcyqhZ9yZsazoHfHfxa5H+rXFv7YRUdpMGAGHz5As80SfqQcBCIjzxb0I16b/iv8dkXvWzJH5EDdWN3/jnIzIcmolfzGO1hyGPS7XrTRoaULCWZB6KIH8BW1fZHkYi0IpNpDFsqtVsEcgytGcQKrFLhDVkhUuA5m1bM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746483808; c=relaxed/simple; bh=M3gOJF8FbIPNH7gnh+YiNGAF+azqNqWc3tUWY7cigN0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=H0KNlVVO4sAJF4FxTWhETC9Hx/Xzl7nuSEUomFA3X1qKzz1agdMdwR4NiPUs+uW1YJcx8N8i30Q8gZsIeujuu3bW2dVcEk7mXxIAKYiD4OUlXhpq3Kil6wD5RIbzrPmF6VqIpeGSgfJHih9ScxWVzxye7qdYME/D+IrWAefHoBk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=khwClrlj; 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="khwClrlj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB9A4C4CEE4; Mon, 5 May 2025 22:23:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746483807; bh=M3gOJF8FbIPNH7gnh+YiNGAF+azqNqWc3tUWY7cigN0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=khwClrljQV/16Z13hyP3591HnjJXGVJvvnJT6YqsO3SEiHVLtIWM9jC3EkK2jvcVp lj7DkwpfCERmv2aCZb8FDGUy4Q0fOO6W73LpSKSTwkWFqGL/HzHY3KcQ2XpRCyF0KA FfbWN7//sZlO0CZz2tYA4DrMcqVdHo69bWiyfS6gUHpXKxDkF1Mhb0bayUcwWjMbzs V2/fyglM6GHbe8Hevqd/yfb87zwSmltLVAmG9YBaF9B/gEv+edUFcpmaRtdyxCpJCA wxuqBx3vKPgrQVMGZsIBv2IjhIDpycPpIoEnM6zZ/5YOnOAmvj4RXbppfTXDKggDDV Rh0vNGSNfiIPA== 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 6.14 226/642] ALSA: seq: Improve data consistency at polling Date: Mon, 5 May 2025 18:07:22 -0400 Message-Id: <20250505221419.2672473-226-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250505221419.2672473-1-sashal@kernel.org> References: <20250505221419.2672473-1-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 6.14.5 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 706f53e39b53c..7f03e1ec92355 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1150,8 +1150,7 @@ 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; } @@ -2586,8 +2585,6 @@ 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 20155e3e87c6a..ccde0ca3d2082 100644 --- a/sound/core/seq/seq_memory.c +++ b/sound/core/seq/seq_memory.c @@ -427,6 +427,7 @@ 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