Replace the deprecated[1] strncpy() with strnlen() on the source followed by memcpy(). Normally strscpy() would be used in this case, but skel_internal.h is shared between kernel and userspace tools, and strscpy() is not available in the userspace build context.
The source map_name is a NUL-terminated C string (the only caller passes the "__loader.map" 12 character string literal). The destination attr.map_name is char[BPF_OBJ_NAME_LEN] (16 bytes) in union bpf_attr, ultimately passed to the bpf() syscall. The bpf(BPF_MAP_CREATE) syscall, through bpf_obj_name_cpy(), requires a NUL terminator within this 16-byte array, rejecting names that use all 16 bytes. Valid names are therefore at most 15 characters, but this wasn't being checked via the skel_map_create() path. Add a matching check and refuse 16+ character strings early, as they would be refused later by bpf_obj_name_cpy(). The attr is pre-zeroed with memset() at the top of the function, so the last byte of attr.map_name is always NUL, meaning the memcpy() of just the non-NUL characters from the source will always produce a NUL-terminated destination string. Link: https://github.com/KSPP/linux/issues/90 [1] Signed-off-by: Kees Cook <[email protected]> --- v3: instead of truncation, refuse the long length (test appears to have been a flake) v2: https://lore.kernel.org/lkml/[email protected]/ v1: https://lore.kernel.org/lkml/[email protected]/ Cc: Alexei Starovoitov <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: sun jian <[email protected]> Cc: Andrii Nakryiko <[email protected]> Cc: Eduard Zingerman <[email protected]> Cc: Daniel Borkmann <[email protected]> Cc: Martin KaFai Lau <[email protected]> Cc: Song Liu <[email protected]> Cc: Yonghong Song <[email protected]> Cc: John Fastabend <[email protected]> Cc: KP Singh <[email protected]> Cc: Stanislav Fomichev <[email protected]> Cc: Hao Luo <[email protected]> Cc: <[email protected]> --- tools/lib/bpf/skel_internal.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h index 6a8f5c7a02eb..2d38c387f43c 100644 --- a/tools/lib/bpf/skel_internal.h +++ b/tools/lib/bpf/skel_internal.h @@ -236,6 +236,7 @@ static inline int skel_map_create(enum bpf_map_type map_type, { const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size); union bpf_attr attr; + size_t map_name_len; memset(&attr, 0, attr_sz); @@ -243,7 +244,12 @@ static inline int skel_map_create(enum bpf_map_type map_type, attr.excl_prog_hash = (unsigned long) excl_prog_hash; attr.excl_prog_hash_size = excl_prog_hash_sz; - strncpy(attr.map_name, map_name, sizeof(attr.map_name)); + /* attr.map_name must be NUL-terminated, like bpf_obj_name_cpy() */ + map_name_len = strnlen(map_name, sizeof(attr.map_name)); + if (map_name_len == sizeof(attr.map_name)) + return -EINVAL; + memcpy(attr.map_name, map_name, map_name_len); + attr.key_size = key_size; attr.value_size = value_size; attr.max_entries = max_entries; -- 2.34.1
