[lkml]   [2019]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 1/3] Fix backward-ring-buffer.c format-truncation error
Perf does not build with the ubsan (undefined behavior sanitizer)
and there is an error that says:

tests/backward-ring-buffer.c:23:45: error: ‘%d’ directive output
may be truncated writing between 1 and 10 bytes into a region of
size 8 [-Werror=format-truncation=]
snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);

This can be reproduced by running (from the tip directory):
make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined"

Th error occurs because they are writing to the 10 byte buffer - the
index 'i' of the for loop and the 2 byte hardcoded string. If somehow 'i'
was greater than 8 bytes (10 - 2), then the snprintf function would
truncate the string. Increasing the size of the buffer fixes the error.

Signed-off-by: Numfor Mbiziwo-Tiapo <>
tools/perf/tests/backward-ring-buffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
index 6d598cc071ae..1a9c3becf5ff 100644
--- a/tools/perf/tests/backward-ring-buffer.c
+++ b/tools/perf/tests/backward-ring-buffer.c
@@ -18,7 +18,7 @@ static void testcase(void)
int i;

for (i = 0; i < NR_ITERS; i++) {
- char proc_name[10];
+ char proc_name[15];

snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);
prctl(PR_SET_NAME, proc_name);
 \ /
  Last update: 2019-07-24 20:46    [W:0.077 / U:0.952 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site