bpf: Sanitize the bpf_struct_ops tcp-cc name

The bpf_struct_ops tcp-cc name should be sanitized in order to
avoid problematic chars (e.g. whitespaces).

This patch reuses the bpf_obj_name_cpy() for accepting the same set
of characters in order to keep a consistent bpf programming experience.
A "size" param is added.  Also, the strlen is returned on success so
that the caller (like the bpf_tcp_ca here) can error out on empty name.
The existing callers of the bpf_obj_name_cpy() only need to change the
testing statement to "if (err < 0)".  For all these existing callers,
the err will be overwritten later, so no extra change is needed
for the new strlen return value.

v3:
  - reverse xmas tree style
v2:
  - Save the orig_src to avoid "end - size" (Andrii)

Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200314010209.1131542-1-kafai@fb.com

1 files changed, 2 insertions, 5 deletions

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 574972bc7299..2bf3abeb1456 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -184,7 +184,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
 {
 	const struct tcp_congestion_ops *utcp_ca;
 	struct tcp_congestion_ops *tcp_ca;
-	size_t tcp_ca_name_len;
 	int prog_fd;
 	u32 moff;
 
@@ -199,13 +198,11 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
 		tcp_ca->flags = utcp_ca->flags;
 		return 1;
 	case offsetof(struct tcp_congestion_ops, name):
-		tcp_ca_name_len = strnlen(utcp_ca->name, sizeof(utcp_ca->name));
-		if (!tcp_ca_name_len ||
-		    tcp_ca_name_len == sizeof(utcp_ca->name))
+		if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
+				     sizeof(tcp_ca->name)) <= 0)
 			return -EINVAL;
 		if (tcp_ca_find(utcp_ca->name))
 			return -EEXIST;
-		memcpy(tcp_ca->name, utcp_ca->name, sizeof(tcp_ca->name));
 		return 1;
 	}