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comedi: Fix initialization of data for instructions that write to subdevice

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commit 46d8c744136ce2454aa4c35c138cc06817f92b8e upstream.

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: ed9eccbe89 ("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>
This commit is contained in:
Ian Abbott
2025-07-07 17:14:39 +01:00
committed by Greg Kroah-Hartman
parent 10f9024a8c
commit 673ee92bd2
1 changed files with 12 additions and 2 deletions
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14
drivers/comedi/comedi_fops.c
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@@ -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)