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 0D87D449EBB for ; Wed, 13 May 2026 14:34:36 +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=1778682877; cv=none; b=ZHK+QKEPlTo6XTspLLfmVf5DCPF74wltnnMli9sXkNK6P/iAAzSMbxsvmEtypKh88mSSOUzovUHf04J6Xkd0ywRNrBP6L7bR1cehWfdkYyBSC9vvYmGdIvj2B2goEZweuGaaRDvwoFPr0amzIQXHlqZ0CldNL9TYDi4D6sTwZdE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778682877; c=relaxed/simple; bh=8DN6coJTPUxuqrpo4XenHfxMg55z27zILPTOyVh/F3I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c4PD9D61k5sdEtXuk7A++miNnywdYEZ4FNXYdTUTy0uuNAFA8aI7Hw9PtNrVYmHrSuzsL8YbnqOChb/n6x6gIh16Fca3G/GAwzaKXfImE6aMHA2T6muRwW34j8KffT2uIpzEaTfk2XVYojMFBESvnFSyuR/OLp8oNmA23J8lo/A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=u3JEDfJy; 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="u3JEDfJy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20246C2BCF7; Wed, 13 May 2026 14:34:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778682876; bh=8DN6coJTPUxuqrpo4XenHfxMg55z27zILPTOyVh/F3I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u3JEDfJyOoYm1uPFXxjycISEGMhzHCu4m0aIpm8kius+mxFrIZ1bgyB1gLRqzv2nQ vh6at66HYCD/JaegtPazSoijevEPCwEyFA5w+zCp6IaHK/B2o1i5xVb7RVwdJm/z+Z KOk6LRyLoBLQhaTx0gF+iz4QGHWJqCn5HTup/vPHmcP/qmrL0HaMcwAeKFvea50I0a RPWrkU2qeFBvB37CD/U/L7y4/XMf7QIIPVtzK5ZXJkc4a5g/htY9TD+v1PqSv+Z1Oo jRyu6uPknzK0m7mRaL+KVSMjYHDkH8xwUV9SEA+CODTJ1YDCdBiK6vAcQbqmfJF11d x1+8MVcOB5SDQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Takashi Iwai , Jake Lamberson , Sasha Levin Subject: [PATCH 6.1.y 2/3] ALSA: core: Fix potential data race at fasync handling Date: Wed, 13 May 2026 10:34:32 -0400 Message-ID: <20260513143433.3755085-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260513143433.3755085-1-sashal@kernel.org> References: <2026051252-doozy-thyself-9752@gregkh> <20260513143433.3755085-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Takashi Iwai [ Upstream commit 8146cd333d235ed32d48bb803fdf743472d7c783 ] 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 Stable-dep-of: 5337213381df ("ALSA: core: Serialize deferred fasync state checks") Signed-off-by: Sasha Levin --- sound/core/misc.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/sound/core/misc.c b/sound/core/misc.c index a6dd4d38a46b3..918d59a541c82 100644 --- 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); @@ -229,7 +233,10 @@ void snd_fasync_free(struct snd_fasync *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); } -- 2.53.0