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

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 49b1a70..212991f 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -160,6 +160,7 @@ static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
 }
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
                           bool lock_src);
+int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size);
 
 struct bpf_offload_dev;
 struct bpf_offloaded_map;

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0c7fb0d..2857b7d 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -696,14 +696,15 @@ int bpf_get_file_flag(int flags)
                   offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
                   sizeof(attr->CMD##_LAST_FIELD)) != NULL
 
-/* dst and src must have at least BPF_OBJ_NAME_LEN number of bytes.
- * Return 0 on success and < 0 on error.
+/* dst and src must have at least "size" number of bytes.
+ * Return strlen on success and < 0 on error.
  */
-static int bpf_obj_name_cpy(char *dst, const char *src)
+int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size)
 {
-       const char *end = src + BPF_OBJ_NAME_LEN;
+       const char *end = src + size;
+       const char *orig_src = src;
 
-       memset(dst, 0, BPF_OBJ_NAME_LEN);
+       memset(dst, 0, size);
        /* Copy all isalnum(), '_' and '.' chars. */
        while (src < end && *src) {
                if (!isalnum(*src) &&
@@ -712,11 +713,11 @@ static int bpf_obj_name_cpy(char *dst, const char *src)
                *dst++ = *src++;
        }
 
-       /* No '\0' found in BPF_OBJ_NAME_LEN number of bytes */
+       /* No '\0' found in "size" number of bytes */
        if (src == end)
                return -EINVAL;
 
-       return 0;
+       return src - orig_src;
 }
 
 int map_check_no_btf(const struct bpf_map *map,
@@ -810,8 +811,9 @@ static int map_create(union bpf_attr *attr)
        if (IS_ERR(map))
                return PTR_ERR(map);
 
-       err = bpf_obj_name_cpy(map->name, attr->map_name);
-       if (err)
+       err = bpf_obj_name_cpy(map->name, attr->map_name,
+                              sizeof(attr->map_name));
+       if (err < 0)
                goto free_map;
 
        atomic64_set(&map->refcnt, 1);
@@ -2098,8 +2100,9 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
                goto free_prog;
 
        prog->aux->load_time = ktime_get_boottime_ns();
-       err = bpf_obj_name_cpy(prog->aux->name, attr->prog_name);
-       if (err)
+       err = bpf_obj_name_cpy(prog->aux->name, attr->prog_name,
+                              sizeof(attr->prog_name));
+       if (err < 0)
                goto free_prog;
 
        /* run eBPF verifier */

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 574972b..2bf3abe 100644 (file)
--- 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;
        }