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 9FBAE556BB9 for ; Fri, 11 Sep 2026 19:47:26 +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=1789156058; cv=none; b=a3JNB/1/kOXMRUKsCo3Y6c6Z2gZj1mC1ZWGoiQbafzQyEl+R7fj8TyHpa8nHNJjn9O8z6GSahVQ2ZpvXjKmPIkqrjksWAPr+0ckMGwInJtUY8Crb1VmqUqUiRh2symcon2DyAsmXJzoRgPbAEtOSJNGTv/4BInwaxkGFRJP0CRw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156058; c=relaxed/simple; bh=cyMmIqMgFhKvQ/0rQ1T9zEp6PRdsor+GUdvUHaOnnxI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pM9V/hJKS6DymAlMSqYj72+d2HN8WAO3nvKDxXFCwZnEeV5iLr6qc2//N2k51REYtTjYM4C6o9gv1eckTDPtJJ6vQckx1G5qcXaHZI7epYtFLnpWlqWy1TyqRcSyQHL59250WEA7UT3a3LUgQ77LqnRKLKqrjWkT5yeB3T/BDF0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TGCYKyHk; 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="TGCYKyHk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA4991F000FF; Fri, 11 Sep 2026 19:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156046; bh=33CUlx4eVwkyQP4PK7dFw8qjFfxp35z2NK6QcfT8jy4=; h=From:To:Cc:Subject:Date:Reply-To; b=TGCYKyHkeN6t51+2A8nCFtMVJFuScsTBeyPkV9TaJQs5R36Nc25hTWPYROmLw5oKK FdAD4egP5Nr3KC3MzcvjnvImbqL0LNh8rJLczGHWB0BjM+s8Ak5WSz7h0s03JePhz/ E0qlBHUkHDpXz+5flyoeMF6iRXQitaKigxfGq/CE= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80970: ALSA: FCP: do not copy out an uninitialised init response Date: Fri, 11 Sep 2026 21:41:16 +0200 Message-ID: <2026091144-CVE-2026-80970-bfeb@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3997; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=wuHJy/YZPKtnJXm+4VRZpeHkcOBbOhUKmO5OUYzwIcw=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIm2+v9pYuPwD29yDCixZM7PsWz0f1Ackl6wyXXHcJ Iybw/5rRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAEzk/R2GeSafNd48q9v2lfNg pU/Nm4JdO7nZzjHMj9UP+JQsfCNGc4/N11t5dcJ7+LR3AgA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: ALSA: FCP: do not copy out an uninitialised init response fcp_ioctl_init() allocates its response buffer with kmalloc() and copies the whole buffer back to userspace: buf_size = init.step0_resp_size + init.step2_resp_size; void *resp __free(kfree) = kmalloc(buf_size, GFP_KERNEL); ... if (copy_to_user(arg->resp, resp, buf_size)) return -EFAULT; Nothing clears the buffer, and the only writer of its leading step0_resp_size bytes is the step-0 control transfer: err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), FCP_USB_REQ_STEP0, USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN, 0, private->bInterfaceNumber, step0_resp, private->step0_resp_size); if (err < 0) return err; usb_fill_control_urb() does not set URB_SHORT_NOT_OK, so a short or zero-length data stage completes with status 0 and snd_usb_ctl_msg() returns a small actual_length. The only check is err < 0, so a short transfer is accepted as success. snd_usb_ctl_msg() copies the full size back unconditionally: buf = kmemdup(data, size, GFP_KERNEL); ... memcpy(data, buf, size); Bytes the device never wrote are therefore restored into resp unchanged and copied to userspace. step0_resp_size and step2_resp_size are each validated only to 1..255, so the caller also picks the slab cache, from kmalloc-8 up to kmalloc-512. On 7.2.0-rc5 (arm64), device answering step 0 with a zero-length data stage, s0 = s2 = 255: # init_on_alloc off, no spray step0 window [0,255): nonzero=94/255 000: 00 80 60 06 00 00 ff ff 18 00 00 00 57 01 ea 01 010: 08 78 22 13 00 00 ff ff a8 c4 5f 80 00 80 ff ff # same kernel, kmalloc-512 pre-seeded with an 8-byte tag step0 window [0,255): nonzero=219/255 tagbytes=232 # identical run, init_on_alloc=1 step0 window [0,255): nonzero=0/255 tagbytes=0 # all three runs step2 window [255,510): device words matched=62/62 a8 c4 5f 80 00 80 ff ff is the little-endian kernel text address ffff8000805fc4a8. The step-2 window is unaffected, so the disclosure is exactly the step-0 region. Zero the buffer, and require the step-0 transfer to deliver the full step0_resp_size bytes so a short data stage is reported as an error. Discovered by XBOW, triaged by Baul Lee The Linux kernel CVE team has assigned CVE-2026-80970 to this issue. Affected and fixed versions =========================== Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 7.2.4 with commit 29ab2df278ab4f1d238cd9c1c393ee00db175cba Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 7.3-rc1 with commit 4335e387786479889e6db691fe06d345e52ea536 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-80970 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: sound/usb/fcp.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/29ab2df278ab4f1d238cd9c1c393ee00db175cba https://git.kernel.org/stable/c/4335e387786479889e6db691fe06d345e52ea536