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Subject[PATCH AUTOSEL 4.19 08/15] staging: greybus: loopback_test: fix potential path truncations
From: Johan Hovold <>

[ Upstream commit ae62cf5eb2792d9a818c2d93728ed92119357017 ]

Newer GCC warns about possible truncations of two generated path names as
we're concatenating the configurable sysfs and debugfs path prefixes
with a filename and placing the results in buffers of the same size as
the maximum length of the prefixes.

snprintf(d->name, MAX_STR_LEN, "gb_loopback%u", dev_id);

snprintf(d->sysfs_entry, MAX_SYSFS_PATH, "%s%s/",
t->sysfs_prefix, d->name);

snprintf(d->debugfs_entry, MAX_SYSFS_PATH, "%sraw_latency_%s",
t->debugfs_prefix, d->name);

Fix this by separating the maximum path length from the maximum prefix
length and reducing the latter enough to fit the generated strings.

Note that we also need to reduce the device-name buffer size as GCC
isn't smart enough to figure out that we ever only used MAX_STR_LEN
bytes of it.

Fixes: 6b0658f68786 ("greybus: tools: Add tools directory to greybus repo and add loopback")
Signed-off-by: Johan Hovold <>
Signed-off-by: Greg Kroah-Hartman <>
Signed-off-by: Sasha Levin <>
drivers/staging/greybus/tools/loopback_test.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/greybus/tools/loopback_test.c b/drivers/staging/greybus/tools/loopback_test.c
index c1c344e7391c3..6f444702570e0 100644
--- a/drivers/staging/greybus/tools/loopback_test.c
+++ b/drivers/staging/greybus/tools/loopback_test.c
@@ -21,6 +21,7 @@
#include <signal.h>

#define MAX_NUM_DEVICES 10
+#define MAX_SYSFS_PREFIX 0x80
#define MAX_SYSFS_PATH 0x200
#define CSV_MAX_LINE 0x1000
#define SYSFS_MAX_INT 0x20
@@ -69,7 +70,7 @@ struct loopback_results {

struct loopback_device {
- char name[MAX_SYSFS_PATH];
+ char name[MAX_STR_LEN];
char sysfs_entry[MAX_SYSFS_PATH];
char debugfs_entry[MAX_SYSFS_PATH];
struct loopback_results results;
@@ -95,8 +96,8 @@ struct loopback_test {
int stop_all;
int poll_count;
char test_name[MAX_STR_LEN];
- char sysfs_prefix[MAX_SYSFS_PATH];
- char debugfs_prefix[MAX_SYSFS_PATH];
+ char sysfs_prefix[MAX_SYSFS_PREFIX];
+ char debugfs_prefix[MAX_SYSFS_PREFIX];
struct timespec poll_timeout;
struct loopback_device devices[MAX_NUM_DEVICES];
struct loopback_results aggregate_results;
@@ -915,10 +916,10 @@ int main(int argc, char *argv[])
t.iteration_max = atoi(optarg);
case 'S':
- snprintf(t.sysfs_prefix, MAX_SYSFS_PATH, "%s", optarg);
+ snprintf(t.sysfs_prefix, MAX_SYSFS_PREFIX, "%s", optarg);
case 'D':
- snprintf(t.debugfs_prefix, MAX_SYSFS_PATH, "%s", optarg);
+ snprintf(t.debugfs_prefix, MAX_SYSFS_PREFIX, "%s", optarg);
case 'm':
t.mask = atol(optarg);
@@ -969,10 +970,10 @@ int main(int argc, char *argv[])

if (!strcmp(t.sysfs_prefix, ""))
- snprintf(t.sysfs_prefix, MAX_SYSFS_PATH, "%s", sysfs_prefix);
+ snprintf(t.sysfs_prefix, MAX_SYSFS_PREFIX, "%s", sysfs_prefix);

if (!strcmp(t.debugfs_prefix, ""))
- snprintf(t.debugfs_prefix, MAX_SYSFS_PATH, "%s", debugfs_prefix);
+ snprintf(t.debugfs_prefix, MAX_SYSFS_PREFIX, "%s", debugfs_prefix);

ret = find_loopback_devices(&t);
if (ret)
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