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 9257735CB7C; Fri, 4 Sep 2026 05:43:40 +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=1788500621; cv=none; b=JjzQyBAkhi2Z7y3TRTNsmwXVnkKozMjobkG51KJJywbVP/2gltfPs8B+i30S6yzB9fShJsAxOHfdFvDiBqKrMHpOUzYgI5JQQ8rrj+1GvT+d1mhGlzEDDsWMAwejcVCR0WD9tqHyQsBvpHYj6FS2dautJJW4JMm/RAg3G0y+lD8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500621; c=relaxed/simple; bh=d+cDi/zXe0hZLGLBUO8+NuubwD1RkUaDA50JH1NLmRQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oIAX6QMw8SiQn7qM72T35Y3Zl5zLeJhQRIOem/SQvi/++rk+IGKLpKbSUUSbdJBJOH0RSDcmGdqLZiWG840dfq49SANUKi7+fh8ROCNFCBW5Z+NYxqxnecIN0Nt3NuitbyRvwNktvpDJ6Mar1CXEkg96xTypji/9MoSU2SV7JSk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qENLWUAR; 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="qENLWUAR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB0811F00A3D; Fri, 4 Sep 2026 05:43:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500620; bh=v+tYDL2w3Ipr5cQRM4tSXApab2mGlrQsME47wpRK7ek=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qENLWUARe1WuKSHezxby33hWNIDKkyD51vFGIpqTV/jc+r94m7gABaTkmzRkgYZfw O4kn9J9QYoboIrKLRIrkt5K9fltwb4+XFvjQBs9O4j1antsNrXSFKsBBAjVULAZsWV liQvQ3qVm1gK2VmM/0oMM21WA+ivEkofRXUJbeEk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sonali Pradhan Subject: [PATCH 6.18 078/552] usb: gadget: u_audio: Fix use-after-free on sound card disconnect Date: Fri, 4 Sep 2026 06:53:55 +0200 Message-ID: <20260904045749.629821052@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sonali Pradhan commit 858965947081d10d41d9a1010a540d3d5eea958b upstream. g_audio_cleanup() invokes snd_card_free_when_closed() to initiate sound card teardown and immediately frees the underlying struct snd_uac_chip context. However, snd_card_free_when_closed() returns asynchronously while ALSA control elements (kctls) remain open in userspace. When userspace control applications access or close these open file descriptors, kctl callbacks attempt to dereference kctl->private_data pointing to &uac->c_prm or &uac->p_prm within the freed uac structure, resulting in a use-after-free (UAF) memory corruption. Fix this issue by deferring the destruction of struct snd_uac_chip until all references to the ALSA sound card are released. Register a custom card->private_free callback (u_audio_card_free) during g_audio_setup() that frees uac and its associated playback/capture request and ring buffers only when the sound card reference count drops to zero. Fixes: 6c67ed9ad9b8 ("usb: gadget: u_audio: don't let userspace block driver unbind") Cc: stable@vger.kernel.org Signed-off-by: Sonali Pradhan Link: https://patch.msgid.link/20260810071237.2207680-1-sonalipradhan@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/u_audio.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) --- a/drivers/usb/gadget/function/u_audio.c +++ b/drivers/usb/gadget/function/u_audio.c @@ -1177,6 +1177,20 @@ static struct snd_kcontrol_new u_audio_c }, }; +static void u_audio_card_free(struct snd_card *card) +{ + struct snd_uac_chip *uac = card->private_data; + + if (!uac) + return; + + kfree(uac->p_prm.reqs); + kfree(uac->c_prm.reqs); + kfree(uac->p_prm.rbuf); + kfree(uac->c_prm.rbuf); + kfree(uac); +} + int g_audio_setup(struct g_audio *g_audio, const char *pcm_name, const char *card_name) { @@ -1258,6 +1272,8 @@ int g_audio_setup(struct g_audio *g_audi goto fail; uac->card = card; + card->private_data = uac; + card->private_free = u_audio_card_free; /* * Create first PCM device @@ -1426,6 +1442,8 @@ int g_audio_setup(struct g_audio *g_audi snd_fail: snd_card_free(card); + return err; + fail: kfree(uac->p_prm.reqs); kfree(uac->c_prm.reqs); @@ -1451,12 +1469,6 @@ void g_audio_cleanup(struct g_audio *g_a card = uac->card; if (card) snd_card_free_when_closed(card); - - kfree(uac->p_prm.reqs); - kfree(uac->c_prm.reqs); - kfree(uac->p_prm.rbuf); - kfree(uac->c_prm.rbuf); - kfree(uac); } EXPORT_SYMBOL_GPL(g_audio_cleanup);