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 5E9F6194A67; Tue, 27 May 2025 16:57:11 +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=1748365031; cv=none; b=KMm4lo0Os3YK76y9E5FTmT18tAPWZrqbnQNeAJrVAS5JoDqG+7U2/2HXr+n2WzqJE36EBe5M7ff9z7GahMqytGNakq0lUqgc9GBJsMo5QelX6MROb8ZfjqLG8UDBZGJ5NAAU4oFgYRR1my9X1DrfVeey/Dd6JbNhz/Zo7YXEmbI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748365031; c=relaxed/simple; bh=P7B6ezigUKg+siJepV9VmZlhCv2h8ThXvfS+f2He0JI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ot+zHHXiIUSsaVAqiiiZoO7SIewf/AkVlzc1QzjjHDb7IXpgfWpalxWURNwgV1oCiW98UI/GAQ86rU833XSl7DqkQsgEUgOgNBNTaCl6f1ClOvaNWAPwpelVZQprU5eKNIsHqH9haOE4q9DjHsaHXSf/J8z6v4dfFzptSHuf5y0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ylxxtGqB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ylxxtGqB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C030AC4CEE9; Tue, 27 May 2025 16:57:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1748365031; bh=P7B6ezigUKg+siJepV9VmZlhCv2h8ThXvfS+f2He0JI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ylxxtGqBNGzm9HWuHdjfSWKGr73a8Xg+anhCPIvY4cKa1G5EbqMKf9GTWNNdzzivX J/D9h0bss7a+oU9L2Fe2k8y/EovVFTW7GwaT9Q7xZ3mGoY+ALVYPgoL839u0zDN/0H 4DX8TNrXiAK8Wd15+6FIJqjeaPak5daIIonWOrDg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+2d373c9936c00d7e120c@syzkaller.appspotmail.com, Takashi Iwai , Sasha Levin Subject: [PATCH 6.12 215/626] ALSA: seq: Improve data consistency at polling Date: Tue, 27 May 2025 18:21:48 +0200 Message-ID: <20250527162453.758023963@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250527162445.028718347@linuxfoundation.org> References: <20250527162445.028718347@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ 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 b74de9c0969fc..9e59a97f47472 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1164,8 +1164,7 @@ 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; } @@ -2583,8 +2582,6 @@ 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