From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794048200; b=PJkJ1MFEJ4q/U7KP/jlUEGePKxNwn+gxS2I2VoYeac7typz4/d7wXeCa3zMN1N0P+aC3 Cr6bsQ82xicGcZiC8/Y3lxgBf12b/G0lU9IXRnz0ivjKK55uAXKyDVJ+Vxsv1N2UmrkRY YRckRG2lpCIXxvplp22PDJ6E0vjfW0p+W0Ft21Jor0MRlonudtvka6Nv8oYsBMiMD2ZnP D8YEsvUDECzheadxZSoJRLJGqv6iI64Vn2Rynef3QDsmtbxOvjZLibqdT6/veNG+LbRwH XRIyCUIq2uMgrFX3SnFo2rUbNuhn+zsrvnh7sQw4RA8e3+C849iNHTSnK1PxZjRQXpg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794048200; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=O6X61K8KpPrRqUKG5iWME2w3Lxd5AfoFXQ4DlvQ91H8=; b=psbidNb+BoTbrP6Sqg12pUAWL25oU6AwGB/iH6Hy5d787YQC1lbtaiN4zOV9KeTpsE0E pzGd+iLIp8Snhu+IR/CqVmQ1R7onDBWz++VNpRkO0zdL7oC89pPjE+rFwpAL6LvGcxgrH 1iSMcP+P22mDYznH8boNDgygN20YDKS4NwLuoc10iMpLFsRh5Mp0CJeN3Y26pmeA1XIAv CBc1dRdlyInYDKohIrgIqFf0LIseE0Tzk2XAjni4oyW6YAal7lys3q6EoezjeKbMQMNpo Ly9033KBkcUHu0jq8zq9DE8xKk0M/lp18GtwqOXnMNgckP1rcQ/IjKtTq8yEQpPWbOw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OmlacirE; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 416BB606A32C for ; Sat, 7 Nov 2026 10:43:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OmlacirE Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0F351F0089F; Sat, 7 Nov 2026 10:43:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794048200; bh=O6X61K8KpPrRqUKG5iWME2w3Lxd5AfoFXQ4DlvQ91H8=; h=From:To:Cc:Subject:Date; b=OmlacirE0F4NiUf1c7OZxPAwMN37OJ+NWQxSVjjz9pfxXMfEA3kcURMg3j2Ape/uz I4TsV7YWYBQnT09vIVXhmTU242PKHRQlCyHq8qtpt+Xdb5pMpFhZ6+0b5LOksOHqp/ eZUgaHg6ndSYVcVn49rIY9ORYZCrRLlomGdwJeIEXj866/+uCOkqs77uad1fQgr0DJ V26so8x0OK68xbe/2b/PfkpdlmSsi8gtiTOEv8PfG/Mmr968zL1FhWZyle0JgPcR0v N9eEIYG3VzwFBlniA91MTHosTj81Th2QnIzaboJLUeJ8v2IiFcwJWTYGGbAkw/wtpE GuE6Qi7jDlaAQ== From: Sasha Levin To: tiwai@suse.de, farhad.alemi@berkeley.edu Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] ALSA: control: Fix UAF in snd_ctl_elem_add() on card disconnect" failed to apply to 6.1-stable tree Date: Sat, 7 Nov 2026 05:43:18 -0500 Message-ID: <20261107054318-failed-6.1-d4febca239be@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x d4febca239be3c91498762dd0535a87d4af1eabc # git commit -s git send-email --to '' --in-reply-to '20261107054318-failed-6.1-d4febca239be@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From d4febca239be3c91498762dd0535a87d4af1eabc Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 29 Sep 2026 14:53:42 +0200 Subject: [PATCH] ALSA: control: Fix UAF in snd_ctl_elem_add() on card disconnect A use-after-free can be triggered via SNDRV_CTL_IOCTL_ELEM_ADD when a USB audio card is disconnected while an ELEM_ADD ioctl is in flight. The reproducer parks the ioctl thread inside copy_from_user() using userfaultfd, then tears down the USB device. Unlike every other ALSA control _user handler (ELEM_INFO, ELEM_READ, ELEM_WRITE, TLV_*), snd_ctl_elem_add_user() never calls snd_power_ref_and_wait(), so the parked thread holds no power reference. snd_card_disconnect() therefore cannot observe it via snd_power_sync_ref() and proceeds unimpeded: 1. card->shutdown is set to 1 2. device_del(&card->card_dev) drops the kobject reference on the parent USB interface device (card->dev = &intf->dev) 3. The USB core drops its own reference and calls device_release(), freeing the struct usb_interface, including the embedded struct device that card->dev points to When the userfaultfd is resolved and the thread resumes, snd_ctl_elem_add() acquires controls_rwsem without checking card->shutdown and calls __snd_ctl_add_replace(). Because the reproducer pre-registered the same control, the CTL_ADD_EXCLUSIVE path calls dev_err(card->dev, ...) on the freed USB interface: KASAN: slab-use-after-free Read in __dev_printk Add a card->shutdown guard immediately after acquiring controls_rwsem in snd_ctl_elem_add(). At that point card->shutdown is guaranteed to be stable: snd_card_disconnect() sets it before freeing the parent device, and it never transitions back to 0. A thread that acquired the lock before disconnect sees shutdown=0 and holds the write lock through the rest of the operation, preventing concurrent disconnect from proceeding past its own controls_rwsem-less shutdown=1 store (which happened earlier, outside the lock) from racing with dev_err(). Reported-by: Farhad Alemi Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai Link: https://patch.msgid.link/20260929125346.1478631-3-tiwai@suse.de --- sound/core/control.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/core/control.c b/sound/core/control.c index 4199342d4ffe0..535ceba294acf 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -1802,6 +1802,8 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, alloc_size = compute_user_elem_size(private_size, count); guard(rwsem_write)(&card->controls_rwsem); + if (card->shutdown) + return -ENODEV; if (check_user_elem_overflow(card, alloc_size)) return -ENOMEM; -- 2.53.0