6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ian Abbott abbotti@mev.co.uk
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 stable@kernel.org # 5.13+ Signed-off-by: Ian Abbott abbotti@mev.co.uk Link: https://lore.kernel.org/r/20250725141034.87297-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/comedi/drivers.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)
--- a/drivers/comedi/drivers.c +++ b/drivers/comedi/drivers.c @@ -619,11 +619,9 @@ static int insn_rw_emulate_bits(struct c unsigned int chan = CR_CHAN(insn->chanspec); unsigned int base_chan = (chan < 32) ? 0 : chan; unsigned int _data[2]; + unsigned int i; int ret;
- if (insn->n == 0) - return 0; - memset(_data, 0, sizeof(_data)); memset(&_insn, 0, sizeof(_insn)); _insn.insn = INSN_BITS; @@ -634,18 +632,21 @@ static int insn_rw_emulate_bits(struct c if (insn->insn == INSN_WRITE) { if (!(s->subdev_flags & SDF_WRITABLE)) return -EINVAL; - _data[0] = 1U << (chan - base_chan); /* mask */ - _data[1] = data[0] ? (1U << (chan - base_chan)) : 0; /* bits */ + _data[0] = 1U << (chan - base_chan); /* mask */ } + for (i = 0; i < insn->n; i++) { + if (insn->insn == INSN_WRITE) + _data[1] = data[i] ? _data[0] : 0; /* bits */ + + ret = s->insn_bits(dev, s, &_insn, _data); + if (ret < 0) + return ret;
- ret = s->insn_bits(dev, s, &_insn, _data); - if (ret < 0) - return ret; - - if (insn->insn == INSN_READ) - data[0] = (_data[1] >> (chan - base_chan)) & 1; + if (insn->insn == INSN_READ) + data[i] = (_data[1] >> (chan - base_chan)) & 1; + }
- return 1; + return insn->n; }
static int __comedi_device_postconfig_async(struct comedi_device *dev,