bpf, bpftool: fix a few ubsan warnings

The issue is reported at https://github.com/libbpf/libbpf/issues/28.

Basically, per C standard, for
  void *memcpy(void *dest, const void *src, size_t n)
if "dest" or "src" is NULL, regardless of whether "n" is 0 or not,
the result of memcpy is undefined. clang ubsan reported three such
instances in bpf.c with the following pattern:
  memcpy(dest, 0, 0).

Although in practice, no known compiler will cause issues when
copy size is 0. Let us still fix the issue to silence ubsan
warnings.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 9 insertions, 10 deletions

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c039094ad3aa..dababce68f0b 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -79,7 +79,6 @@ static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size)
 
 int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 {
-        __u32 name_len = create_attr->name ? strlen(create_attr->name) : 0;
         union bpf_attr attr;
 
         memset(&attr, '\0', sizeof(attr));
@@ -89,8 +88,9 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
         attr.value_size = create_attr->value_size;
         attr.max_entries = create_attr->max_entries;
         attr.map_flags = create_attr->map_flags;
-        memcpy(attr.map_name, create_attr->name,
-               min(name_len, BPF_OBJ_NAME_LEN - 1));
+        if (create_attr->name)
+                memcpy(attr.map_name, create_attr->name,
+                       min(strlen(create_attr->name), BPF_OBJ_NAME_LEN - 1));
         attr.numa_node = create_attr->numa_node;
         attr.btf_fd = create_attr->btf_fd;
         attr.btf_key_type_id = create_attr->btf_key_type_id;
@@ -155,7 +155,6 @@ int bpf_create_map_in_map_node(enum bpf_map_type map_type, const char *name,
                                int key_size, int inner_map_fd, int max_entries,
                                __u32 map_flags, int node)
 {
-        __u32 name_len = name ? strlen(name) : 0;
         union bpf_attr attr;
 
         memset(&attr, '\0', sizeof(attr));
@@ -166,7 +165,9 @@ int bpf_create_map_in_map_node(enum bpf_map_type map_type, const char *name,
         attr.inner_map_fd = inner_map_fd;
         attr.max_entries = max_entries;
         attr.map_flags = map_flags;
-        memcpy(attr.map_name, name, min(name_len, BPF_OBJ_NAME_LEN - 1));
+        if (name)
+                memcpy(attr.map_name, name,
+                       min(strlen(name), BPF_OBJ_NAME_LEN - 1));
 
         if (node >= 0) {
                 attr.map_flags |= BPF_F_NUMA_NODE;
@@ -216,7 +217,6 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
         void *finfo = NULL, *linfo = NULL;
         union bpf_attr attr;
         __u32 log_level;
-        __u32 name_len;
         int fd;
 
         if (!load_attr || !log_buf != !log_buf_sz)
@@ -226,8 +226,6 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
         if (log_level > (4 | 2 | 1) || (log_level && !log_buf))
                 return -EINVAL;
 
-        name_len = load_attr->name ? strlen(load_attr->name) : 0;
-
         memset(&attr, 0, sizeof(attr));
         attr.prog_type = load_attr->prog_type;
         attr.expected_attach_type = load_attr->expected_attach_type;
@@ -253,8 +251,9 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
         attr.line_info_rec_size = load_attr->line_info_rec_size;
         attr.line_info_cnt = load_attr->line_info_cnt;
         attr.line_info = ptr_to_u64(load_attr->line_info);
-        memcpy(attr.prog_name, load_attr->name,
-               min(name_len, BPF_OBJ_NAME_LEN - 1));
+        if (load_attr->name)
+                memcpy(attr.prog_name, load_attr->name,
+                       min(strlen(load_attr->name), BPF_OBJ_NAME_LEN - 1));
 
         fd = sys_bpf_prog_load(&attr, sizeof(attr));
         if (fd >= 0)