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 3135E307491; Tue, 26 Aug 2025 13:37:21 +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=1756215441; cv=none; b=c/zZPMpgMUSExsOqcPowEERTW7UiBokXOdxaaOm4KHRobHWjB0Qerj5z50UrHZRENOu0BRWXo/dZ3vtY9utkbmL/nVybh/ohyRRHIMZC3Y3EeLT22C+EJYU1YDs3I7AGzJcPCfuuxoqcx9mOrtYw2F5RCUPxd13nfJaA5rY+8Zc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756215441; c=relaxed/simple; bh=I2pVXxW8DdNiXWOqwSDqr55enDCW7uLAJrmXmh/OZq4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VM75Cg4l9kYtXwXXGGvowVFjoYgQ6L8zb/dhuTXTezFl5gBIuAgLZGLePxp/HvsGyZ9l+4vjAjwt6k3bYMLMtKaDDAvVIUb+9pQSQa6SnXozuvUOc63K4zBMLpH7YLIQrQXlq4977BeTQac86VGCCyRYhnBxFGeXde9rdb6+y20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0YEk3pN2; 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="0YEk3pN2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A910AC4CEF1; Tue, 26 Aug 2025 13:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756215441; bh=I2pVXxW8DdNiXWOqwSDqr55enDCW7uLAJrmXmh/OZq4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0YEk3pN2Ckc2LincOG8SSPq3Dx9xk5e54s7YiQXvqeu92Z2KjHiwoIpzVbpqJhkH5 V6AadPQ/9uRQQHsiPT9mqoT9LXT77SrqGYZt3Sdhc90ohPqatzpV2dnLbRJL/LGyRo DVFwBHhOCfOWhliDmBTOYZhoYaDJZTGbampPKMC8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+cb96ec476fb4914445c9@syzkaller.appspotmail.com, Ian Abbott Subject: [PATCH 5.15 035/644] comedi: Fix use of uninitialized data in insn_rw_emulate_bits() Date: Tue, 26 Aug 2025 13:02:06 +0200 Message-ID: <20250826110947.380691641@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110946.507083938@linuxfoundation.org> References: <20250826110946.507083938@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ian Abbott commit e9cb26291d009243a4478a7ffb37b3a9175bfce9 upstream. For Comedi `INSN_READ` and `INSN_WRITE` instructions on "digital" subdevices (subdevice types `COMEDI_SUBD_DI`, `COMEDI_SUBD_DO`, and `COMEDI_SUBD_DIO`), it is common for the subdevice driver not to have `insn_read` and `insn_write` handler functions, but to have an `insn_bits` handler function for handling Comedi `INSN_BITS` instructions. In that case, the subdevice's `insn_read` and/or `insn_write` function handler pointers are set to point to the `insn_rw_emulate_bits()` function by `__comedi_device_postconfig()`. For `INSN_WRITE`, `insn_rw_emulate_bits()` currently assumes that the supplied `data[0]` value is a valid copy from user memory. It will at least exist because `do_insnlist_ioctl()` and `do_insn_ioctl()` in "comedi_fops.c" ensure at lease `MIN_SAMPLES` (16) elements are allocated. However, if `insn->n` is 0 (which is allowable for `INSN_READ` and `INSN_WRITE` instructions, then `data[0]` may contain uninitialized data, and certainly contains invalid data, possibly from a different instruction in the array of instructions handled by `do_insnlist_ioctl()`. This will result in an incorrect value being written to the digital output channel (or to the digital input/output channel if configured as an output), and may be reflected in the internal saved state of the channel. Fix it by returning 0 early if `insn->n` is 0, before reaching the code that accesses `data[0]`. Previously, the function always returned 1 on success, but it is supposed to be the number of data samples actually read or written up to `insn->n`, which is 0 in this case. Reported-by: syzbot+cb96ec476fb4914445c9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=cb96ec476fb4914445c9 Fixes: ed9eccbe8970 ("Staging: add comedi core") Cc: stable@vger.kernel.org # 5.13+ Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20250707153355.82474-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman --- drivers/comedi/drivers.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/comedi/drivers.c +++ b/drivers/comedi/drivers.c @@ -615,6 +615,9 @@ static int insn_rw_emulate_bits(struct c unsigned int _data[2]; int ret; + if (insn->n == 0) + return 0; + memset(_data, 0, sizeof(_data)); memset(&_insn, 0, sizeof(_insn)); _insn.insn = INSN_BITS;