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 A0FF73FF1D5; Fri, 15 May 2026 15:58:55 +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=1778860735; cv=none; b=NWikKEG9F1dHZOhc27ANukeiC6ApKeB4WFJZU5Aonpw4PBtWmVISRp8uUinl5QN5WHWlygireC5hEzMzrAUjHu0FxeqZXH6241U0OwKzTOg4HzyuJau2W26+z3uzSAtP4hbRvROGn6GTdtl33dImtkV769lbNu0H85rBZJFm9PQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778860735; c=relaxed/simple; bh=1lZgyaoN1pbsWe0t4JSzxHLYnm8tapYO4IUfRk9yXqY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uB/Rv4s09SdliDDXEx0fG/UiIz+HRIbK4c/UhzfDZ+6zU/xoOalbLZc+kLXJvLVL8JiqV0SnGXCWMRmHuAPbf6WKF3I9WnEtqjH6KW8Xm8dSGbNwtwE4u0S/6CNj2W4SwY4vkVyr2FaeLIy0mjNvlUnUZzo8glEdWrSI4fJCNRk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=r1ClYVoK; 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="r1ClYVoK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3738CC2BCC7; Fri, 15 May 2026 15:58:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778860735; bh=1lZgyaoN1pbsWe0t4JSzxHLYnm8tapYO4IUfRk9yXqY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r1ClYVoKPEF7dxIZMf4BfYVZmNTg5uTCRCetzC3WWjtdjF6eQVS9ZbBlQE35Tt9cL 1wviHO/vji313vK4w/UKR1cr0HJLTr0p+rEqvFR/CN0hUKEiwfK7lItYmxrdoZthpa eAHRHbUI6qmNKr42dEniGtlwVm+oPxehkhzHjWdw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jake Lamberson , Takashi Iwai Subject: [PATCH 6.6 058/474] ALSA: core: Fix potential data race at fasync handling Date: Fri, 15 May 2026 17:42:47 +0200 Message-ID: <20260515154716.300062538@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260515154715.053014143@linuxfoundation.org> References: <20260515154715.053014143@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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); }