linux-stable.git/drivers/comedi, branch linux-6.16.y

comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()

2025-08-28T14:34:40+00:00

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

comedi: pcl726: Prevent invalid irq number

2025-08-28T14:34:40+00:00

commit 96cb948408b3adb69df7e451ba7da9d21f814d00 upstream.

The reproducer passed in an irq number(0x80008000) that was too large,
which triggered the oob.

Added an interrupt number check to prevent users from passing in an irq
number that was too large.

If `it->options[1]` is 31, then `1 << it->options[1]` is still invalid
because it shifts a 1-bit into the sign bit (which is UB in C).
Possible solutions include reducing the upper bound on the
`it->options[1]` value to 30 or lower, or using `1U << it->options[1]`.

The old code would just not attempt to request the IRQ if the
`options[1]` value were invalid.  And it would still configure the
device without interrupts even if the call to `request_irq` returned an
error.  So it would be better to combine this test with the test below.

Fixes: fff46207245c ("staging: comedi: pcl726: enable the interrupt support code")
Cc: stable  # 5.13+
Reported-by: syzbot+5cd373521edd68bebcb3@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5cd373521edd68bebcb3
Tested-by: syzbot+5cd373521edd68bebcb3@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis 
Reviewed-by: Ian Abbott 
Link: https://lore.kernel.org/r/tencent_3C66983CC1369E962436264A50759176BF09@qq.com
Signed-off-by: Greg Kroah-Hartman

comedi: Make insn_rw_emulate_bits() do insn->n samples

2025-08-28T14:34:40+00:00

commit 7afba9221f70d4cbce0f417c558879cba0eb5e66 upstream.

The `insn_rw_emulate_bits()` function is used as a default handler for
`INSN_READ` instructions for subdevices that have a handler for
`INSN_BITS` but not for `INSN_READ`.  Similarly, it is used as a default
handler for `INSN_WRITE` instructions for subdevices that have a handler
for `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the
`INSN_READ` or `INSN_WRITE` instruction handling with a constructed
`INSN_BITS` instruction.  However, `INSN_READ` and `INSN_WRITE`
instructions are supposed to be able read or write multiple samples,
indicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently
only handles a single sample.  For `INSN_READ`, the comedi core will
copy `insn->n` samples back to user-space.  (That triggered KASAN
kernel-infoleak errors when `insn->n` was greater than 1, but that is
being fixed more generally elsewhere in the comedi core.)

Make `insn_rw_emulate_bits()` either handle `insn->n` samples, or return
an error, to conform to the general expectation for `INSN_READ` and
`INSN_WRITE` handlers.

Fixes: ed9eccbe8970 ("Staging: add comedi core")
Cc: stable  # 5.13+
Signed-off-by: Ian Abbott 
Link: https://lore.kernel.org/r/20250725141034.87297-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: fix race between polling and detaching

2025-08-20T16:41:37+00:00

commit 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2 upstream.

syzbot reports a use-after-free in comedi in the below link, which is
due to comedi gladly removing the allocated async area even though poll
requests are still active on the wait_queue_head inside of it. This can
cause a use-after-free when the poll entries are later triggered or
removed, as the memory for the wait_queue_head has been freed.  We need
to check there are no tasks queued on any of the subdevices' wait queues
before allowing the device to be detached by the `COMEDI_DEVCONFIG`
ioctl.

Tasks will read-lock `dev->attach_lock` before adding themselves to the
subdevice wait queue, so fix the problem in the `COMEDI_DEVCONFIG` ioctl
handler by write-locking `dev->attach_lock` before checking that all of
the subdevices are safe to be deleted.  This includes testing for any
sleepers on the subdevices' wait queues.  It remains locked until the
device has been detached.  This requires the `comedi_device_detach()`
function to be refactored slightly, moving the bulk of it into new
function `comedi_device_detach_locked()`.

Note that the refactor of `comedi_device_detach()` results in
`comedi_device_cancel_all()` now being called while `dev->attach_lock`
is write-locked, which wasn't the case previously, but that does not
matter.

Thanks to Jens Axboe for diagnosing the problem and co-developing this
patch.

Cc: stable 
Fixes: 2f3fdcd7ce93 ("staging: comedi: add rw_semaphore to protect against device detachment")
Link: https://lore.kernel.org/all/687bd5fe.a70a0220.693ce.0091.GAE@google.com/
Reported-by: syzbot+01523a0ae5600aef5895@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=01523a0ae5600aef5895
Co-developed-by: Jens Axboe 
Signed-off-by: Jens Axboe 
Signed-off-by: Ian Abbott 
Tested-by: Jens Axboe 
Link: https://lore.kernel.org/r/20250722155316.27432-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: comedi_test: Fix possible deletion of uninitialized timers

2025-07-16T13:02:44+00:00

In `waveform_common_attach()`, the two timers `&devpriv->ai_timer` and
`&devpriv->ao_timer` are initialized after the allocation of the device
private data by `comedi_alloc_devpriv()` and the subdevices by
`comedi_alloc_subdevices()`.  The function may return with an error
between those function calls.  In that case, `waveform_detach()` will be
called by the Comedi core to clean up.  The check that
`waveform_detach()` uses to decide whether to delete the timers is
incorrect.  It only checks that the device private data was allocated,
but that does not guarantee that the timers were initialized.  It also
needs to check that the subdevices were allocated.  Fix it.

Fixes: 73e0e4dfed4c ("staging: comedi: comedi_test: fix timer lock-up")
Cc: stable@vger.kernel.org # 6.15+
Signed-off-by: Ian Abbott 
Link: https://lore.kernel.org/r/20250708130627.21743-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

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

2025-07-16T13:02:44+00:00

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 
Link: https://lore.kernel.org/r/20250707161439.88385-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: Fix use of uninitialized data in insn_rw_emulate_bits()

2025-07-16T13:02:44+00:00

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

comedi: das6402: Fix bit shift out of bounds

2025-07-16T13:02:44+00:00

When checking for a supported IRQ number, the following test is used:

	/* IRQs 2,3,5,6,7, 10,11,15 are valid for "enhanced" mode */
	if ((1 << it->options[1]) & 0x8cec) {

However, `it->options[i]` is an unchecked `int` value from userspace, so
the shift amount could be negative or out of bounds.  Fix the test by
requiring `it->options[1]` to be within bounds before proceeding with
the original test.  Valid `it->options[1]` values that select the IRQ
will be in the range [1,15]. The value 0 explicitly disables the use of
interrupts.

Fixes: 79e5e6addbb1 ("staging: comedi: das6402: rewrite broken driver")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott 
Link: https://lore.kernel.org/r/20250707135737.77448-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: aio_iiro_16: Fix bit shift out of bounds

2025-07-16T13:02:44+00:00

When checking for a supported IRQ number, the following test is used:

	if ((1 << it->options[1]) & 0xdcfc) {

However, `it->options[i]` is an unchecked `int` value from userspace, so
the shift amount could be negative or out of bounds.  Fix the test by
requiring `it->options[1]` to be within bounds before proceeding with
the original test.  Valid `it->options[1]` values that select the IRQ
will be in the range [1,15]. The value 0 explicitly disables the use of
interrupts.

Fixes: ad7a370c8be4 ("staging: comedi: aio_iiro_16: add command support for change of state detection")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott 
Link: https://lore.kernel.org/r/20250707134622.75403-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: pcl812: Fix bit shift out of bounds

2025-07-16T13:02:44+00:00

When checking for a supported IRQ number, the following test is used:

	if ((1 << it->options[1]) & board->irq_bits) {

However, `it->options[i]` is an unchecked `int` value from userspace, so
the shift amount could be negative or out of bounds.  Fix the test by
requiring `it->options[1]` to be within bounds before proceeding with
the original test.  Valid `it->options[1]` values that select the IRQ
will be in the range [1,15]. The value 0 explicitly disables the use of
interrupts.

Reported-by: syzbot+32de323b0addb9e114ff@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=32de323b0addb9e114ff
Fixes: fcdb427bc7cf ("Staging: comedi: add pcl821 driver")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott 
Link: https://lore.kernel.org/r/20250707133429.73202-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman