tools: iio: iio_generic_buffer: Fix read size

[ Upstream commit 7c919b619bcc68158921b1bd968f0e704549bbb6 ]

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@dc75zzyyyyyyyyyyyyycy-3.rev.dnainternet.fi/
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@gmail.com>
Link: https://lore.kernel.org/r/Y0kMh0t5qUXJw3nQ@dc75zzyyyyyyyyyyyyycy-3.rev.dnainternet.fi
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c
index 2491c54..f8deae4 100644 (file)
--- 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) {