[ Upstream commit a195cefff49f60054998333e81ee95170ce8bf92 ]
GCC 9 fails to calculate the size of local constant strings and produces a false positive:
samples/bpf/task_fd_query_user.c: In function ‘test_debug_fs_uprobe’: samples/bpf/task_fd_query_user.c:242:67: warning: ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size 215 [-Wformat-truncation=] 242 | snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s/id", | ^~ 243 | event_type, event_alias); | ~~~~~~~~~~~ samples/bpf/task_fd_query_user.c:242:2: note: ‘snprintf’ output between 45 and 300 bytes into a destination of size 256 242 | snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s/id", | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 243 | event_type, event_alias); | ~~~~~~~~~~~~~~~~~~~~~~~~
Workaround this by lowering the buffer size to a reasonable value. Related GCC Bugzilla: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83431
Signed-off-by: Matteo Croce mcroce@redhat.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin sashal@kernel.org --- samples/bpf/task_fd_query_user.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/samples/bpf/task_fd_query_user.c b/samples/bpf/task_fd_query_user.c index aff2b4ae914e..e39938058223 100644 --- a/samples/bpf/task_fd_query_user.c +++ b/samples/bpf/task_fd_query_user.c @@ -216,7 +216,7 @@ static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return) { const char *event_type = "uprobe"; struct perf_event_attr attr = {}; - char buf[256], event_alias[256]; + char buf[256], event_alias[sizeof("test_1234567890")]; __u64 probe_offset, probe_addr; __u32 len, prog_id, fd_type; int err, res, kfd, efd;