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 5B876221704; Tue, 26 Aug 2025 13:11:38 +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=1756213899; cv=none; b=GVeuP0nQMzQoUsZsTxWdi4nSAXcuriPnRsTPoFXubZlN3PXjAIb1Jz6VJFMMPQc+iigfKdTh7mTYEPHAOXLW0bARxbCf7wEcpYSITa+RQ4ncX1j34KMKiOuYGdUpoLcrmBPYag3ZbFX+YWr/V5ehW+pZCdcC2Ze7dVHlc0csraQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756213899; c=relaxed/simple; bh=BFFImIJSLPvQ2ApktTqGOTr9aL4tv8B8h6GeX5dMzpY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jvXMRxjvgbIsb1EYZPH3ZDUD/DZ/myVpOgwqToi4khLqFA79v0VI2Y9JNhOne9HXUCjdEHaHunmtQpuQZHpY9Txol7po90xKj686msHAYVNXJ9FJ/1bLnn64rSYNzlwSlfJteGj0m3v6RmRm89Vs11PhHmbtdbJ9rrEEXYpWyQk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pujPGAEb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="pujPGAEb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C0B5C4CEF1; Tue, 26 Aug 2025 13:11:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756213898; bh=BFFImIJSLPvQ2ApktTqGOTr9aL4tv8B8h6GeX5dMzpY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pujPGAEbp0O2A3r0cQSG5AbyzrC+5zXNYbfVdQOZinE2QI05Tm/sbhEvCzEQmTaUv 9bOnRAyyHNivco5BE8kYUvaA4p1pSqyHyveC12bFJ6TF+FGeoO/PMnQDEhyrDPKWvB pJfX5siDvPvAxXJEOw9wKsppaTwl+QikdMgUk65w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+a5e45f768aab5892da5d@syzkaller.appspotmail.com, syzbot+fb4362a104d45ab09cf9@syzkaller.appspotmail.com, Arnaud Lecomte , Ian Abbott , stable Subject: [PATCH 6.6 522/587] comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() Date: Tue, 26 Aug 2025 13:11:11 +0200 Message-ID: <20250826111006.276383670@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110952.942403671@linuxfoundation.org> References: <20250826110952.942403671@linuxfoundation.org> User-Agent: quilt/0.68 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ian Abbott commit 3cd212e895ca2d58963fdc6422502b10dd3966bb upstream. syzbot reports a KMSAN kernel-infoleak in `do_insn_ioctl()`. A kernel buffer is allocated to hold `insn->n` samples (each of which is an `unsigned int`). For some instruction types, `insn->n` samples are copied back to user-space, unless an error code is being returned. The problem is that not all the instruction handlers that need to return data to userspace fill in the whole `insn->n` samples, so that there is an information leak. There is a similar syzbot report for `do_insnlist_ioctl()`, although it does not have a reproducer for it at the time of writing. One culprit is `insn_rw_emulate_bits()` which is used as the handler for `INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have a specific handler for that instruction, but do have an `INSN_BITS` handler. For `INSN_READ` it only fills in at most 1 sample, so if `insn->n` is greater than 1, the remaining `insn->n - 1` samples copied to userspace will be uninitialized kernel data. Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. It never returns an error, even if it fails to fill the buffer. Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure that uninitialized parts of the allocated buffer are zeroed before handling each instruction. Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fix replaced the call to `kmalloc_array()` with `kcalloc()`, but it is not always necessary to clear the whole buffer. Fixes: ed9eccbe8970 ("Staging: add comedi core") Reported-by: syzbot+a5e45f768aab5892da5d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a5e45f768aab5892da5d Reported-by: syzbot+fb4362a104d45ab09cf9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=fb4362a104d45ab09cf9 Cc: stable # 5.13+ Cc: Arnaud Lecomte Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20250725125324.80276-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman --- drivers/comedi/comedi_fops.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/comedi/comedi_fops.c +++ b/drivers/comedi/comedi_fops.c @@ -1587,6 +1587,9 @@ static int do_insnlist_ioctl(struct come memset(&data[n], 0, (MIN_SAMPLES - n) * sizeof(unsigned int)); } + } else { + memset(data, 0, max_t(unsigned int, n, MIN_SAMPLES) * + sizeof(unsigned int)); } ret = parse_insn(dev, insns + i, data, file); if (ret < 0) @@ -1670,6 +1673,8 @@ static int do_insn_ioctl(struct comedi_d memset(&data[insn->n], 0, (MIN_SAMPLES - insn->n) * sizeof(unsigned int)); } + } else { + memset(data, 0, n_data * sizeof(unsigned int)); } ret = parse_insn(dev, insn, data, file); if (ret < 0)