On 4/10/19 12:58 AM, Daniel Borkmann wrote: > On 04/10/2019 02:37 AM, Yonghong Song wrote: >> 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@xxxxxx> > > Applied, thanks. I fixed up $SUBJECT while applying to add a subsystem prefix. > >> --- >> tools/lib/bpf/bpf.c | 19 +++++++++---------- >> 1 file changed, 9 insertions(+), 10 deletions(-) >> >> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c >> index a1db869a6fda..78f2400dd2d1 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)); > > Any reason we don't simplify this to use strncpy() for all these occurrences? No particular reason, just did not think that far :-) Yes, strncpy instead of memcpy should work here as well. > > Thanks, > Daniel >
