linux-kernel - [PATCH AUTOSEL 5.15 05/31] tools: iio: iio_generic

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Date:   Wed, 23 Nov 2022 07:42:06 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Matti Vaittinen <mazziesaccount@...il.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Sasha Levin <sashal@...nel.org>, jic23@...nel.org,
        linux-iio@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 05/31] tools: iio: iio_generic_buffer: Fix read size

From: Matti Vaittinen <mazziesaccount@...il.com>

[ 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@...il.com>
Link: https://lore.kernel.org/r/Y0kMh0t5qUXJw3nQ@dc75zzyyyyyyyyyyyyycy-3.rev.dnainternet.fi
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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) {
-- 
2.35.1