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Subject[PATCH AUTOSEL 4.9 3/7] staging: greybus: loopback_test: fix potential path truncation
From: Johan Hovold <>

[ Upstream commit f16023834863932f95dfad13fac3fc47f77d2f29 ]

Newer GCC warns about a possible truncation of a generated sysfs path
name as we're concatenating a directory path with a file name and
placing the result in a buffer that is half the size of the maximum
length of the directory path (which is user controlled).

loopback_test.c: In function 'open_poll_files':
loopback_test.c:651:31: warning: '%s' directive output may be truncated writing up to 511 bytes into a region of size 255 [-Wformat-truncation=]
651 | snprintf(buf, sizeof(buf), "%s%s", dev->sysfs_entry, "iteration_count");
| ^~
loopback_test.c:651:3: note: 'snprintf' output between 16 and 527 bytes into a destination of size 255
651 | snprintf(buf, sizeof(buf), "%s%s", dev->sysfs_entry, "iteration_count");
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by making sure the buffer is large enough the concatenated

Fixes: 6b0658f68786 ("greybus: tools: Add tools directory to greybus repo and add loopback")
Fixes: 9250c0ee2626 ("greybus: Loopback_test: use poll instead of inotify")
Signed-off-by: Johan Hovold <>
Signed-off-by: Greg Kroah-Hartman <>
Signed-off-by: Sasha Levin <>
drivers/staging/greybus/tools/loopback_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/greybus/tools/loopback_test.c b/drivers/staging/greybus/tools/loopback_test.c
index f7f4cd6fb55b3..9430f3e0162b5 100644
--- a/drivers/staging/greybus/tools/loopback_test.c
+++ b/drivers/staging/greybus/tools/loopback_test.c
@@ -646,7 +646,7 @@ int find_loopback_devices(struct loopback_test *t)
static int open_poll_files(struct loopback_test *t)
struct loopback_device *dev;
- char buf[MAX_STR_LEN];
char dummy;
int fds_idx = 0;
int i;
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