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 AE5B955C315 for ; Fri, 11 Sep 2026 19:47:46 +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=1789156069; cv=none; b=fVK6b4kAIJ9u6gGYiR7b+H1LVCBGoZjvDSUE652xnOa2Q0juWV56xZT5su6oDQl57EGgfYrsQReJ4asbw43onMNna0Pw2u4Zg6xTbYgG9xHpeYlSwDSSnAR85UM1RP8i9ovr+IqMuVicZBMCmZltk0cchG8iSG04vXG6I5Qr88o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156069; c=relaxed/simple; bh=yLMGn5hwL//P+O2t5Le6FhAK8n5NbcpBlwk8eAeH3gM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=dyIVNhhYd8U73/tUSyNNRp18unnWJ+XoH3PsorddnoHK/bJ7L3m0uyP7iWjm5K1/G3oKPeoTb1i/P+H79mSgbxKYtNmMc34tOBZFIP/EQy0k6dGlkhg3JJB15jpyGBh2eXOGNbzdv2ev90+n9xigxcfxE5hbPCwLJDL8Urzb2J8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0dWb4nGk; 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="0dWb4nGk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 984991F00893; Fri, 11 Sep 2026 19:47:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156064; bh=1egKEkccbzg4u4m9+qNAdixvRpI/7QdaAa4YpKY99Ms=; h=From:To:Cc:Subject:Date:Reply-To; b=0dWb4nGkIY6tLO3Xb3KMj9Y2nAWQtKNMOGLxJAXTC6Be/ess+fMcTuwytXSCJivSp kDLrjqlrruOwsiPJYZ44LMLoFcoml0FA/E8qLHQeEPr99vvD0IFCAsX5sLPhDsmtoQ XpYbmVYSV5zFFnOUytIugqHwBtAV6d5z1oZwy+S4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80975: mfd: qnap-mcu: keep the reply buffer alive past a command timeout Date: Fri, 11 Sep 2026 21:41:21 +0200 Message-ID: <2026091145-CVE-2026-80975-3dc8@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=3648; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=hrSAzu6QA6z0OPgFq4Lc6XZgn8se7ApG7oj3E3BNaA4=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIm2D/xxjNtE9maT5nCvR5MTXKdJX+6xuFyul8BrVR T3PzubriGVhEGRikBVTZPmyjefo/opDil6Gtqdh5rAygQxh4OIUgIlcCGCYZyCU6/T5WlBRkdra eaImKw9uCtl9imEOP9e8W42Szx3XvC9pePzEVKHhttx+AA== 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: mfd: qnap-mcu: keep the reply buffer alive past a command timeout qnap_mcu_exec() publishes an on-stack buffer to the receive path: unsigned char rx[QNAP_MCU_RX_BUFFER_SIZE]; ... reply->data = rx; reply->length = length; and qnap_mcu_receive_buf() writes into it from the serdev receive path, which runs out of flush_to_ldisc() and is not serialized against qnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec() holds that mutex across wait_for_completion_timeout(). On a timeout qnap_mcu_exec() returns with reply->data still pointing at its own frame. A reply that arrives late, or an unsolicited message from the MCU, is then written into a stack frame that has been left, corrupting whatever runs next on that stack. The same applies when qnap_mcu_write() fails, since that path returns without touching the reply state either. Move the receive buffer into struct qnap_mcu. It is 37 bytes and the structure is devm_kzalloc()ed, so it lives as long as the driver, and a late write lands in memory that is still valid and is reinitialized by the next command. bus_lock keeps commands from sharing it. This deliberately does not clear reply->data or reply->length on the timeout path. Doing so races with qnap_mcu_receive_buf(), which reads both after its if (!reply->length) return size; check: clearing reply->data gives a NULL dereference, and clearing reply->length alone removes the reply->received == reply->length exit condition, so the copy loop runs until the uart chunk is consumed and overruns the buffer. Leaving both set keeps the write bounded by reply->length, which qnap_mcu_exec() has already checked against sizeof(mcu->rx). The Linux kernel CVE team has assigned CVE-2026-80975 to this issue. Affected and fixed versions =========================== Issue introduced in 6.14 with commit 998f70d1806bb718a7565f350283e4a79c8cbb4b and fixed in 6.18.51 with commit 0b6680e306397097a97767447368221fac753809 Issue introduced in 6.14 with commit 998f70d1806bb718a7565f350283e4a79c8cbb4b and fixed in 7.2.4 with commit 8391ee06d08845a0a165b5fe679ba326915166b2 Issue introduced in 6.14 with commit 998f70d1806bb718a7565f350283e4a79c8cbb4b and fixed in 7.3-rc1 with commit 47504742cea7878ebd1bf1491bbed923df6b90b1 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-2026-80975 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: drivers/mfd/qnap-mcu.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/0b6680e306397097a97767447368221fac753809 https://git.kernel.org/stable/c/8391ee06d08845a0a165b5fe679ba326915166b2 https://git.kernel.org/stable/c/47504742cea7878ebd1bf1491bbed923df6b90b1