From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1B23034BA42; Sat, 30 May 2026 16:52:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780159962; cv=none; b=cBI3vtWb5kRf64IuJEEiCxI5JLfl/qfxKJKL70KYhDEWdCnA2gM8E729UB8KyBqzsgjo7KXFYqv00+p56fquW26dEV0wyqeKXKfUygbE16qpyzvaEYBQdEWyYPqgU2XqDXK7WGz63ob1UnEmJMm6rd4iSItKrNZH5X7Qg0DY6bI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780159962; c=relaxed/simple; bh=I+ET57xotEeYD+nX1StFkEkFqeSTsbFHx6UbiF5OR+c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NRusEvXajm3EVo+gJrKt1Rul3OanYEFFZyMS+W+UkA6OW6KQfLFrSJ99jrSHZkIAYDgs+mqrsrfidOjhTs3swrY5zJ9vMAXXFZBalBxgQCETkYV3bgmZvY7se8JtVmcb1Kl4qCt+VhyM2/NgOJgswQ2NKr7UEtiKJNKfAXYOJQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gmuZBWrl; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gmuZBWrl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A9671F00898; Sat, 30 May 2026 16:52:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780159961; bh=MMFUTwOegvBTk6EG/u4jxlk9fbWbF01BQpov4wnWIr0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gmuZBWrloCyoxhyACzJedM2sQY2P9mVbtxU1nIrJXAdjOzjV+1L37/M+QRSCUVzXB Qma8d5OzskZLOd8jfMEdN/UFz+ljsAvQzbF0FreQeTlPlPjgZX7iJraFmaVCeM2cC9 Uv1OMLftONNa9tCE+7Mr8yFNGVJMkfo6lEt8Upp4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jake Lamberson , Takashi Iwai Subject: [PATCH 6.1 208/969] ALSA: core: Fix potential data race at fasync handling Date: Sat, 30 May 2026 17:55:32 +0200 Message-ID: <20260530160306.212054588@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160300.485627683@linuxfoundation.org> References: <20260530160300.485627683@linuxfoundation.org> User-Agent: quilt/0.69 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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 8146cd333d235ed32d48bb803fdf743472d7c783 upstream. In snd_fasync_work_fn(), which is the offload work for traversing and processing the pending fasync list, the call of kill_fasync() is done outside the snd_fasync_lock for avoiding deadlocks. The problem is that its the references of fasync->on, fasync->signal and fasync->poll are done there also outside the lock. Since these may be modified by snd_kill_fasync() call concurrently from other process, inconsistent values might be passed to kill_fasync(). Although there shouldn't be critical UAF, it's still better to be addressed. This patch moves the kill_fasync() argument evaluations inside the snd_fasync_lock for avoiding the data races above. The handling in fasync->on flag is optimized in the loop to skip directly. Also, for more clarity, snd_fasync_free() takes the lock and unlink the pending entry more directly instead of clearing fasync->on flag. Reported-by: Jake Lamberson Fixes: ef34a0ae7a26 ("ALSA: core: Add async signal helpers") Cc: Link: https://patch.msgid.link/20260420061721.3253644-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/misc.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/sound/core/misc.c +++ b/sound/core/misc.c @@ -171,14 +171,18 @@ static LIST_HEAD(snd_fasync_list); static void snd_fasync_work_fn(struct work_struct *work) { struct snd_fasync *fasync; + int signal, poll; spin_lock_irq(&snd_fasync_lock); while (!list_empty(&snd_fasync_list)) { fasync = list_first_entry(&snd_fasync_list, struct snd_fasync, list); list_del_init(&fasync->list); + if (!fasync->on) + continue; + signal = fasync->signal; + poll = fasync->poll; spin_unlock_irq(&snd_fasync_lock); - if (fasync->on) - kill_fasync(&fasync->fasync, fasync->signal, fasync->poll); + kill_fasync(&fasync->fasync, signal, poll); spin_lock_irq(&snd_fasync_lock); } spin_unlock_irq(&snd_fasync_lock); @@ -234,7 +238,10 @@ void snd_fasync_free(struct snd_fasync * { if (!fasync) return; - fasync->on = 0; + + scoped_guard(spinlock_irq, &snd_fasync_lock) + list_del_init(&fasync->list); + flush_work(&snd_fasync_work); kfree(fasync); }