The fd_array attribute of the BPF_PROG_LOAD syscall may contain a set
of file descriptors: maps or btfs. This field was introduced as a
sparse array. Introduce a new attribute, fd_array_cnt, which, if
present, indicates that the fd_array is a continuous array of the
corresponding length.
If fd_array_cnt is non-zero, then every map in the fd_array will be
bound to the program, as if it was used by the program. This
functionality is similar to the BPF_PROG_BIND_MAP syscall, but such
maps can be used by the verifier during the program load.
Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 10 +++
kernel/bpf/syscall.c | 2 +-
kernel/bpf/verifier.c | 107 ++++++++++++++++++++++++++++-----
tools/include/uapi/linux/bpf.h | 10 +++
4 files changed, 114 insertions(+), 15 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4162afc6b5d0..2acf9b336371 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1573,6 +1573,16 @@ union bpf_attr {
* If provided, prog_flags should have BPF_F_TOKEN_FD flag set.
*/
__s32 prog_token_fd;
+ /* The fd_array_cnt can be used to pass the length of the
+ * fd_array array. In this case all the [map] file descriptors
+ * passed in this array will be bound to the program, even if
+ * the maps are not referenced directly. The functionality is
+ * similar to the BPF_PROG_BIND_MAP syscall, but maps can be
+ * used by the verifier during the program load. If provided,
+ * then the fd_array[0,...,fd_array_cnt-1] is expected to be
+ * continuous.
+ */
+ __u32 fd_array_cnt;
};
struct { /* anonymous struct used by BPF_OBJ_* commands */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 58190ca724a2..7e3fbc23c742 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2729,7 +2729,7 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
}
/* last field in 'union bpf_attr' used by this command */
-#define BPF_PROG_LOAD_LAST_FIELD prog_token_fd
+#define BPF_PROG_LOAD_LAST_FIELD fd_array_cnt
static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
{
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 45c11d9cee60..2e262f6516b3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19192,22 +19192,10 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
return 0;
}
-/* Add map behind fd to used maps list, if it's not already there, and return
- * its index.
- * Returns <0 on error, or >= 0 index, on success.
- */
-static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd)
+static int add_used_map(struct bpf_verifier_env *env, struct bpf_map *map)
{
- CLASS(fd, f)(fd);
- struct bpf_map *map;
int i, err;
- map = __bpf_map_get(f);
- if (IS_ERR(map)) {
- verbose(env, "fd %d is not pointing to valid bpf_map\n", fd);
- return PTR_ERR(map);
- }
-
/* check whether we recorded this map already */
for (i = 0; i < env->used_map_cnt; i++)
if (env->used_maps[i] == map)
@@ -19238,6 +19226,24 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd)
return env->used_map_cnt - 1;
}
+/* Add map behind fd to used maps list, if it's not already there, and return
+ * its index.
+ * Returns <0 on error, or >= 0 index, on success.
+ */
+static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd)
+{
+ struct bpf_map *map;
+ CLASS(fd, f)(fd);
+
+ map = __bpf_map_get(f);
+ if (IS_ERR(map)) {
+ verbose(env, "fd %d is not pointing to valid bpf_map\n", fd);
+ return PTR_ERR(map);
+ }
+
+ return add_used_map(env, map);
+}
+
/* find and rewrite pseudo imm in ld_imm64 instructions:
*
* 1. if it accesses map FD, replace it with actual map pointer.
@@ -22537,6 +22543,76 @@ struct btf *bpf_get_btf_vmlinux(void)
return btf_vmlinux;
}
+/*
+ * The add_fd_from_fd_array() is executed only if fd_array_cnt is given. In
+ * this case expect that every file descriptor in the array is either a map or
+ * a BTF, or a hole (0). Everything else is considered to be trash.
+ */
+static int add_fd_from_fd_array(struct bpf_verifier_env *env, int fd)
+{
+ struct bpf_map *map;
+ CLASS(fd, f)(fd);
+ int ret;
+
+ map = __bpf_map_get(f);
+ if (IS_ERR(map)) {
+ if (!IS_ERR(__btf_get_by_fd(f)))
+ return 0;
+
+ /* allow holes */
+ if (!fd)
+ return 0;
+
+ verbose(env, "fd %d is not pointing to valid bpf_map or btf\n", fd);
+ return PTR_ERR(map);
+ }
+
+ ret = add_used_map(env, map);
+ if (ret < 0)
+ return ret;
+ return 0;
+}
+
+static int env_init_fd_array(struct bpf_verifier_env *env, union bpf_attr *attr, bpfptr_t uattr)
+{
+ int size = sizeof(int) * attr->fd_array_cnt;
+ int *copy;
+ int ret;
+ int i;
+
+ if (attr->fd_array_cnt >= MAX_USED_MAPS)
+ return -E2BIG;
+
+ env->fd_array = make_bpfptr(attr->fd_array, uattr.is_kernel);
+
+ /*
+ * The only difference between old (no fd_array_cnt is given) and new
+ * APIs is that in the latter case the fd_array is expected to be
+ * continuous and is scanned for map fds right away
+ */
+ if (!size)
+ return 0;
+
+ copy = kzalloc(size, GFP_KERNEL);
+ if (!copy)
+ return -ENOMEM;
+
+ if (copy_from_bpfptr_offset(copy, env->fd_array, 0, size)) {
+ ret = -EFAULT;
+ goto free_copy;
+ }
+
+ for (i = 0; i < attr->fd_array_cnt; i++) {
+ ret = add_fd_from_fd_array(env, copy[i]);
+ if (ret)
+ goto free_copy;
+ }
+
+free_copy:
+ kfree(copy);
+ return ret;
+}
+
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
{
u64 start_time = ktime_get_ns();
@@ -22568,7 +22644,9 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
env->insn_aux_data[i].orig_idx = i;
env->prog = *prog;
env->ops = bpf_verifier_ops[env->prog->type];
- env->fd_array = make_bpfptr(attr->fd_array, uattr.is_kernel);
+ ret = env_init_fd_array(env, attr, uattr);
+ if (ret)
+ goto err_free_aux_data;
env->allow_ptr_leaks = bpf_allow_ptr_leaks(env->prog->aux->token);
env->allow_uninit_stack = bpf_allow_uninit_stack(env->prog->aux->token);
@@ -22786,6 +22864,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
err_unlock:
if (!is_priv)
mutex_unlock(&bpf_verifier_lock);
+err_free_aux_data:
vfree(env->insn_aux_data);
err_free_env:
kvfree(env);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4162afc6b5d0..2acf9b336371 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1573,6 +1573,16 @@ union bpf_attr {
* If provided, prog_flags should have BPF_F_TOKEN_FD flag set.
*/
__s32 prog_token_fd;
+ /* The fd_array_cnt can be used to pass the length of the
+ * fd_array array. In this case all the [map] file descriptors
+ * passed in this array will be bound to the program, even if
+ * the maps are not referenced directly. The functionality is
+ * similar to the BPF_PROG_BIND_MAP syscall, but maps can be
+ * used by the verifier during the program load. If provided,
+ * then the fd_array[0,...,fd_array_cnt-1] is expected to be
+ * continuous.
+ */
+ __u32 fd_array_cnt;
};
struct { /* anonymous struct used by BPF_OBJ_* commands */
--
2.34.1
