On Fri, 14 Oct 2022 10:15:19 +0300 Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote: > When noevents is true and small buffer is used the allocated memory for > holding the data may be smaller than the hard-coded 64 bytes. This can > cause the iio_generic_buffer to crash. > > Following was recorded on beagle bone black with v6.0 kernel and the > digit fix patch: > https://lore.kernel.org/all/Y0f+tKCz+ZAIoroQ@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > using valgrind; > > ==339== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info > ==339== Command: /iio_generic_buffer -n kx022-accel -T0 -e -l 10 -a -w 2000000 > ==339== Parent PID: 307 > ==339== > ==339== Syscall param read(buf) points to unaddressable byte(s) > ==339== at 0x496BFA4: read (read.c:26) > ==339== by 0x11699: main (iio_generic_buffer.c:724) > ==339== Address 0x4ab3518 is 0 bytes after a block of size 160 alloc'd > ==339== at 0x4864B70: malloc (vg_replace_malloc.c:381) > ==339== by 0x115BB: main (iio_generic_buffer.c:677) > > Fix this by always using the same size for reading as was used for > data storage allocation. > > Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx> > Huh. I have no idea why that value is 64... And git blame says I wrote it over 10 years ago :) Patch looks fine to me, but given I don't understand the logic of the existing code either I'll leave it on list for a little longer before picking it up. > --- > > This patch has been only tested with my kx022a sensor driver. Driver may > have some culprits(s) and my understanding regarding IIO and these tools > is limited so perhaps the hard-coded size of 64 bytes has perfectly > legitimate reason - in which case I would appreciate to hear the > reasoning so I could seek the problem from my driver. Also, I didn't add > the fixes-tag as I don't really know which commit has caused the problem > - as I am not 100% sure what the problem actually is and if I am just > fixing a symptom here. > --- > tools/iio/iio_generic_buffer.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c > index 2491c54a5e4f..f8deae4e26a1 100644 > --- a/tools/iio/iio_generic_buffer.c > +++ b/tools/iio/iio_generic_buffer.c > @@ -715,12 +715,12 @@ int main(int argc, char **argv) > continue; > } > > - toread = buf_len; > } else { > usleep(timedelay); > - toread = 64; > } > > + toread = buf_len; > + > read_size = read(buf_fd, data, toread * scan_size); > if (read_size < 0) { > if (errno == EAGAIN) { > > base-commit: 4fe89d07dcc2804c8b562f6c7896a45643d34b2f
