The patch below does not apply to the 5.4-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 stable@vger.kernel.org.

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-5.4.y git checkout FETCH_HEAD git cherry-pick -x 46d8c744136ce2454aa4c35c138cc06817f92b8e # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025072152-submitter-sterile-1681@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 46d8c744136ce2454aa4c35c138cc06817f92b8e Mon Sep 17 00:00:00 2001 From: Ian Abbott abbotti@mev.co.uk Date: Mon, 7 Jul 2025 17:14:39 +0100 Subject: [PATCH] comedi: Fix initialization of data for instructions that write to subdevice

Some Comedi subdevice instruction handlers are known to access instruction data elements beyond the first `insn->n` elements in some cases. The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions allocate at least `MIN_SAMPLES` (16) data elements to deal with this, but they do not initialize all of that. For Comedi instruction codes that write to the subdevice, the first `insn->n` data elements are copied from user-space, but the remaining elements are left uninitialized. That could be a problem if the subdevice instruction handler reads the uninitialized data. Ensure that the first `MIN_SAMPLES` elements are initialized before calling these instruction handlers, filling the uncopied elements with 0. For `do_insnlist_ioctl()`, the same data buffer elements are used for handling a list of instructions, so ensure the first `MIN_SAMPLES` elements are initialized for each instruction that writes to the subdevice.

Fixes: ed9eccbe8970 ("Staging: add comedi core") Cc: stable@vger.kernel.org # 5.13+ Signed-off-by: Ian Abbott abbotti@mev.co.uk Link: https://lore.kernel.org/r/20250707161439.88385-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c index 962fb9b18a52..c83fd14dd7ad 100644 --- a/drivers/comedi/comedi_fops.c +++ b/drivers/comedi/comedi_fops.c @@ -1556,21 +1556,27 @@ static int do_insnlist_ioctl(struct comedi_device *dev, }

for (i = 0; i < n_insns; ++i) { + unsigned int n = insns[i].n; + if (insns[i].insn & INSN_MASK_WRITE) { if (copy_from_user(data, insns[i].data, - insns[i].n * sizeof(unsigned int))) { + n * sizeof(unsigned int))) { dev_dbg(dev->class_dev, "copy_from_user failed\n"); ret = -EFAULT; goto error; } + if (n < MIN_SAMPLES) { + memset(&data[n], 0, (MIN_SAMPLES - n) * + sizeof(unsigned int)); + } } ret = parse_insn(dev, insns + i, data, file); if (ret < 0) goto error; if (insns[i].insn & INSN_MASK_READ) { if (copy_to_user(insns[i].data, data, - insns[i].n * sizeof(unsigned int))) { + n * sizeof(unsigned int))) { dev_dbg(dev->class_dev, "copy_to_user failed\n"); ret = -EFAULT; @@ -1643,6 +1649,10 @@ static int do_insn_ioctl(struct comedi_device *dev, ret = -EFAULT; goto error; } + if (insn->n < MIN_SAMPLES) { + memset(&data[insn->n], 0, + (MIN_SAMPLES - insn->n) * sizeof(unsigned int)); + } } ret = parse_insn(dev, insn, data, file); if (ret < 0)