From f7c2d64bac1be2ff32f8e4f500c6e5429c1003e0 Mon Sep 17 00:00:00 2001 From: Chang-Hsien Tsai Date: Sun, 19 May 2019 09:05:44 +0000 Subject: samples, bpf: fix to change the buffer size for read() If the trace for read is larger than 4096, the return value sz will be 4096. This results in off-by-one error on buf: static char buf[4096]; ssize_t sz; sz = read(trace_fd, buf, sizeof(buf)); if (sz > 0) { buf[sz] = 0; puts(buf); } Signed-off-by: Chang-Hsien Tsai Signed-off-by: Daniel Borkmann --- samples/bpf/bpf_load.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'samples') diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c index eae7b635343d..6e87cc831e84 100644 --- a/samples/bpf/bpf_load.c +++ b/samples/bpf/bpf_load.c @@ -678,7 +678,7 @@ void read_trace_pipe(void) static char buf[4096]; ssize_t sz; - sz = read(trace_fd, buf, sizeof(buf)); + sz = read(trace_fd, buf, sizeof(buf) - 1); if (sz > 0) { buf[sz] = 0; puts(buf); -- cgit v1.2.3-58-ga151 From a195cefff49f60054998333e81ee95170ce8bf92 Mon Sep 17 00:00:00 2001 From: Matteo Croce Date: Mon, 20 May 2019 23:49:38 +0200 Subject: samples, bpf: suppress compiler warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Daniel Borkmann --- samples/bpf/task_fd_query_user.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'samples') 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; -- cgit v1.2.3-58-ga151