Merge branch 'add-fd_array_cnt-attribute-for-bpf_prog_load'

Anton Protopopov says:

====================
Add fd_array_cnt attribute for BPF_PROG_LOAD

Add a new attribute to the bpf(BPF_PROG_LOAD) system call. If this
new attribute is non-zero, then the fd_array is considered to be a
continuous array of the fd_array_cnt length and to contain only
proper map file descriptors or btf file descriptors.

This change allows maps (and btfs), which aren't referenced directly
by a BPF program, to be bound to the program _and_ also to be present
during the program verification (so BPF_PROG_BIND_MAP is not enough
for this use case).

The primary reason for this change is that it is a prerequisite for
adding "instruction set" maps, which are both non-referenced by the
program and must be present during the program verification.

The first five commits add the new functionality, the sixth adds
corresponding self-tests, and the last one is a small additional fix.

v1 -> v2:
  * rewrite the add_fd_from_fd_array() function (Eduard)
  * a few cleanups in selftests (Eduard)

v2 -> v3:
  * various renamings (Alexei)
  * "0 is not special" (Alexei, Andrii)
  * do not alloc memory on fd_array init (Alexei)
  * fix leaking maps for error path (Hou Tao)
  * use libbpf helpers vs. raw syscalls (Andrii)
  * add comments on __btf_get_by_fd/__bpf_map_get (Alexei)
  * remove extra code (Alexei)

v3 -> v4:
  * simplify error path when parsing fd_array
  * libbpf: pass fd_array_cnt only in prog_load (Alexei)
  * selftests patch contained extra code (Alexei)
  * renames, fix comments (Alexei)

v4 -> v5:
  * Add btfs to env->used_btfs (Andrii)
  * Fix an integer overflow (Andrii)
  * A set of cleanups for selftests (Andrii)
====================

Link: https://patch.msgid.link/20241213130934.1087929-1-aspsk@isovalent.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

3 files changed, 214 insertions, 132 deletions

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e7a59e6462a9..2ef4fef71910 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7746,14 +7746,9 @@ struct btf *btf_get_by_fd(int fd)
 	struct btf *btf;
 	CLASS(fd, f)(fd);
 
-	if (fd_empty(f))
-		return ERR_PTR(-EBADF);
-
-	if (fd_file(f)->f_op != &btf_fops)
-		return ERR_PTR(-EINVAL);
-
-	btf = fd_file(f)->private_data;
-	refcount_inc(&btf->refcnt);
+	btf = __btf_get_by_fd(f);
+	if (!IS_ERR(btf))
+		refcount_inc(&btf->refcnt);
 
 	return btf;
 }
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5684e8ce132d..4e88797fdbeb 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2730,7 +2730,7 @@ 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 c855e7905c35..c0e772996c52 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19218,50 +19218,68 @@ static int find_btf_percpu_datasec(struct btf *btf)
 	return -ENOENT;
 }
 
+/*
+ * Add btf to the used_btfs array and return the index. (If the btf was
+ * already added, then just return the index.) Upon successful insertion
+ * increase btf refcnt, and, if present, also refcount the corresponding
+ * kernel module.
+ */
+static int __add_used_btf(struct bpf_verifier_env *env, struct btf *btf)
+{
+	struct btf_mod_pair *btf_mod;
+	int i;
+
+	/* check whether we recorded this BTF (and maybe module) already */
+	for (i = 0; i < env->used_btf_cnt; i++)
+		if (env->used_btfs[i].btf == btf)
+			return i;
+
+	if (env->used_btf_cnt >= MAX_USED_BTFS)
+		return -E2BIG;
+
+	btf_get(btf);
+
+	btf_mod = &env->used_btfs[env->used_btf_cnt];
+	btf_mod->btf = btf;
+	btf_mod->module = NULL;
+
+	/* if we reference variables from kernel module, bump its refcount */
+	if (btf_is_module(btf)) {
+		btf_mod->module = btf_try_get_module(btf);
+		if (!btf_mod->module) {
+			btf_put(btf);
+			return -ENXIO;
+		}
+	}
+
+	return env->used_btf_cnt++;
+}
+
 /* replace pseudo btf_id with kernel symbol address */
-static int check_pseudo_btf_id(struct bpf_verifier_env *env,
-			       struct bpf_insn *insn,
-			       struct bpf_insn_aux_data *aux)
+static int __check_pseudo_btf_id(struct bpf_verifier_env *env,
+				 struct bpf_insn *insn,
+				 struct bpf_insn_aux_data *aux,
+				 struct btf *btf)
 {
 	const struct btf_var_secinfo *vsi;
 	const struct btf_type *datasec;
-	struct btf_mod_pair *btf_mod;
 	const struct btf_type *t;
 	const char *sym_name;
 	bool percpu = false;
 	u32 type, id = insn->imm;
-	struct btf *btf;
 	s32 datasec_id;
 	u64 addr;
-	int i, btf_fd, err;
-
-	btf_fd = insn[1].imm;
-	if (btf_fd) {
-		btf = btf_get_by_fd(btf_fd);
-		if (IS_ERR(btf)) {
-			verbose(env, "invalid module BTF object FD specified.\n");
-			return -EINVAL;
-		}
-	} else {
-		if (!btf_vmlinux) {
-			verbose(env, "kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\n");
-			return -EINVAL;
-		}
-		btf = btf_vmlinux;
-		btf_get(btf);
-	}
+	int i;
 
 	t = btf_type_by_id(btf, id);
 	if (!t) {
 		verbose(env, "ldimm64 insn specifies invalid btf_id %d.\n", id);
-		err = -ENOENT;
-		goto err_put;
+		return -ENOENT;
 	}
 
 	if (!btf_type_is_var(t) && !btf_type_is_func(t)) {
 		verbose(env, "pseudo btf_id %d in ldimm64 isn't KIND_VAR or KIND_FUNC\n", id);
-		err = -EINVAL;
-		goto err_put;
+		return -EINVAL;
 	}
 
 	sym_name = btf_name_by_offset(btf, t->name_off);
@@ -19269,8 +19287,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 	if (!addr) {
 		verbose(env, "ldimm64 failed to find the address for kernel symbol '%s'.\n",
 			sym_name);
-		err = -ENOENT;
-		goto err_put;
+		return -ENOENT;
 	}
 	insn[0].imm = (u32)addr;
 	insn[1].imm = addr >> 32;
@@ -19278,7 +19295,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 	if (btf_type_is_func(t)) {
 		aux->btf_var.reg_type = PTR_TO_MEM | MEM_RDONLY;
 		aux->btf_var.mem_size = 0;
-		goto check_btf;
+		return 0;
 	}
 
 	datasec_id = find_btf_percpu_datasec(btf);
@@ -19309,8 +19326,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 			tname = btf_name_by_offset(btf, t->name_off);
 			verbose(env, "ldimm64 unable to resolve the size of type '%s': %ld\n",
 				tname, PTR_ERR(ret));
-			err = -EINVAL;
-			goto err_put;
+			return -EINVAL;
 		}
 		aux->btf_var.reg_type = PTR_TO_MEM | MEM_RDONLY;
 		aux->btf_var.mem_size = tsize;
@@ -19319,39 +19335,43 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 		aux->btf_var.btf = btf;
 		aux->btf_var.btf_id = type;
 	}
-check_btf:
-	/* check whether we recorded this BTF (and maybe module) already */
-	for (i = 0; i < env->used_btf_cnt; i++) {
-		if (env->used_btfs[i].btf == btf) {
-			btf_put(btf);
-			return 0;
-		}
-	}
 
-	if (env->used_btf_cnt >= MAX_USED_BTFS) {
-		err = -E2BIG;
-		goto err_put;
-	}
+	return 0;
+}
 
-	btf_mod = &env->used_btfs[env->used_btf_cnt];
-	btf_mod->btf = btf;
-	btf_mod->module = NULL;
+static int check_pseudo_btf_id(struct bpf_verifier_env *env,
+			       struct bpf_insn *insn,
+			       struct bpf_insn_aux_data *aux)
+{
+	struct btf *btf;
+	int btf_fd;
+	int err;
 
-	/* if we reference variables from kernel module, bump its refcount */
-	if (btf_is_module(btf)) {
-		btf_mod->module = btf_try_get_module(btf);
-		if (!btf_mod->module) {
-			err = -ENXIO;
-			goto err_put;
+	btf_fd = insn[1].imm;
+	if (btf_fd) {
+		CLASS(fd, f)(btf_fd);
+
+		btf = __btf_get_by_fd(f);
+		if (IS_ERR(btf)) {
+			verbose(env, "invalid module BTF object FD specified.\n");
+			return -EINVAL;
+		}
+	} else {
+		if (!btf_vmlinux) {
+			verbose(env, "kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\n");
+			return -EINVAL;
 		}
+		btf = btf_vmlinux;
 	}
 
-	env->used_btf_cnt++;
+	err = __check_pseudo_btf_id(env, insn, aux, btf);
+	if (err)
+		return err;
 
+	err = __add_used_btf(env, btf);
+	if (err < 0)
+		return err;
 	return 0;
-err_put:
-	btf_put(btf);
-	return err;
 }
 
 static bool is_tracing_prog_type(enum bpf_prog_type type)
@@ -19368,6 +19388,12 @@ static bool is_tracing_prog_type(enum bpf_prog_type type)
 	}
 }
 
+static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
+{
+	return (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE ||
+		map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
+}
+
 static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 					struct bpf_map *map,
 					struct bpf_prog *prog)
@@ -19446,39 +19472,47 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 			return -EINVAL;
 		}
 
-	return 0;
-}
+	if (bpf_map_is_cgroup_storage(map) &&
+	    bpf_cgroup_storage_assign(env->prog->aux, map)) {
+		verbose(env, "only one cgroup storage of each type is allowed\n");
+		return -EBUSY;
+	}
 
-static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
-{
-	return (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE ||
-		map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
+	if (map->map_type == BPF_MAP_TYPE_ARENA) {
+		if (env->prog->aux->arena) {
+			verbose(env, "Only one arena per program\n");
+			return -EBUSY;
+		}
+		if (!env->allow_ptr_leaks || !env->bpf_capable) {
+			verbose(env, "CAP_BPF and CAP_PERFMON are required to use arena\n");
+			return -EPERM;
+		}
+		if (!env->prog->jit_requested) {
+			verbose(env, "JIT is required to use arena\n");
+			return -EOPNOTSUPP;
+		}
+		if (!bpf_jit_supports_arena()) {
+			verbose(env, "JIT doesn't support arena\n");
+			return -EOPNOTSUPP;
+		}
+		env->prog->aux->arena = (void *)map;
+		if (!bpf_arena_get_user_vm_start(env->prog->aux->arena)) {
+			verbose(env, "arena's user address must be set via map_extra or mmap()\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
 }
 
-/* Add map behind fd to used maps list, if it's not already there, and return
- * its index. Also set *reused to true if this map was already in the list of
- * used maps.
- * Returns <0 on error, or >= 0 index, on success.
- */
-static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reused)
+static int __add_used_map(struct bpf_verifier_env *env, struct bpf_map *map)
 {
-	CLASS(fd, f)(fd);
-	struct bpf_map *map;
-	int i;
-
-	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);
-	}
+	int i, err;
 
 	/* check whether we recorded this map already */
-	for (i = 0; i < env->used_map_cnt; i++) {
-		if (env->used_maps[i] == map) {
-			*reused = true;
+	for (i = 0; i < env->used_map_cnt; i++)
+		if (env->used_maps[i] == map)
 			return i;
-		}
-	}
 
 	if (env->used_map_cnt >= MAX_USED_MAPS) {
 		verbose(env, "The total number of maps per program has reached the limit of %u\n",
@@ -19486,6 +19520,10 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reus
 		return -E2BIG;
 	}
 
+	err = check_map_prog_compatibility(env, map, env->prog);
+	if (err)
+		return err;
+
 	if (env->prog->sleepable)
 		atomic64_inc(&map->sleepable_refcnt);
 
@@ -19496,12 +19534,29 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reus
 	 */
 	bpf_map_inc(map);
 
-	*reused = false;
 	env->used_maps[env->used_map_cnt++] = map;
 
 	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(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.
@@ -19533,7 +19588,6 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 			int map_idx;
 			u64 addr;
 			u32 fd;
-			bool reused;
 
 			if (i == insn_cnt - 1 || insn[1].code != 0 ||
 			    insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
@@ -19594,7 +19648,7 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 				break;
 			}
 
-			map_idx = add_used_map_from_fd(env, fd, &reused);
+			map_idx = add_used_map(env, fd);
 			if (map_idx < 0)
 				return map_idx;
 			map = env->used_maps[map_idx];
@@ -19602,10 +19656,6 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 			aux = &env->insn_aux_data[i];
 			aux->map_index = map_idx;
 
-			err = check_map_prog_compatibility(env, map, env->prog);
-			if (err)
-				return err;
-
 			if (insn[0].src_reg == BPF_PSEUDO_MAP_FD ||
 			    insn[0].src_reg == BPF_PSEUDO_MAP_IDX) {
 				addr = (unsigned long)map;
@@ -19636,39 +19686,6 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 			insn[0].imm = (u32)addr;
 			insn[1].imm = addr >> 32;
 
-			/* proceed with extra checks only if its newly added used map */
-			if (reused)
-				goto next_insn;
-
-			if (bpf_map_is_cgroup_storage(map) &&
-			    bpf_cgroup_storage_assign(env->prog->aux, map)) {
-				verbose(env, "only one cgroup storage of each type is allowed\n");
-				return -EBUSY;
-			}
-			if (map->map_type == BPF_MAP_TYPE_ARENA) {
-				if (env->prog->aux->arena) {
-					verbose(env, "Only one arena per program\n");
-					return -EBUSY;
-				}
-				if (!env->allow_ptr_leaks || !env->bpf_capable) {
-					verbose(env, "CAP_BPF and CAP_PERFMON are required to use arena\n");
-					return -EPERM;
-				}
-				if (!env->prog->jit_requested) {
-					verbose(env, "JIT is required to use arena\n");
-					return -EOPNOTSUPP;
-				}
-				if (!bpf_jit_supports_arena()) {
-					verbose(env, "JIT doesn't support arena\n");
-					return -EOPNOTSUPP;
-				}
-				env->prog->aux->arena = (void *)map;
-				if (!bpf_arena_get_user_vm_start(env->prog->aux->arena)) {
-					verbose(env, "arena's user address must be set via map_extra or mmap()\n");
-					return -EINVAL;
-				}
-			}
-
 next_insn:
 			insn++;
 			i++;
@@ -22839,6 +22856,73 @@ struct btf *bpf_get_btf_vmlinux(void)
 	return btf_vmlinux;
 }
 
+/*
+ * The add_fd_from_fd_array() is executed only if fd_array_cnt is non-zero. In
+ * this case expect that every file descriptor in the array is either a map or
+ * a BTF. 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;
+	struct btf *btf;
+	CLASS(fd, f)(fd);
+	int err;
+
+	map = __bpf_map_get(f);
+	if (!IS_ERR(map)) {
+		err = __add_used_map(env, map);
+		if (err < 0)
+			return err;
+		return 0;
+	}
+
+	btf = __btf_get_by_fd(f);
+	if (!IS_ERR(btf)) {
+		err = __add_used_btf(env, btf);
+		if (err < 0)
+			return err;
+		return 0;
+	}
+
+	verbose(env, "fd %d is not pointing to valid bpf_map or btf\n", fd);
+	return PTR_ERR(map);
+}
+
+static int process_fd_array(struct bpf_verifier_env *env, union bpf_attr *attr, bpfptr_t uattr)
+{
+	size_t size = sizeof(int);
+	int ret;
+	int fd;
+	u32 i;
+
+	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 (!attr->fd_array_cnt)
+		return 0;
+
+	/* Check for integer overflow */
+	if (attr->fd_array_cnt >= (U32_MAX / size)) {
+		verbose(env, "fd_array_cnt is too big (%u)\n", attr->fd_array_cnt);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < attr->fd_array_cnt; i++) {
+		if (copy_from_bpfptr_offset(&fd, env->fd_array, i * size, size))
+			return -EFAULT;
+
+		ret = add_fd_from_fd_array(env, fd);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
 {
 	u64 start_time = ktime_get_ns();
@@ -22870,7 +22954,6 @@ 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);
 
 	env->allow_ptr_leaks = bpf_allow_ptr_leaks(env->prog->aux->token);
 	env->allow_uninit_stack = bpf_allow_uninit_stack(env->prog->aux->token);
@@ -22893,6 +22976,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	if (ret)
 		goto err_unlock;
 
+	ret = process_fd_array(env, attr, uattr);
+	if (ret)
+		goto skip_full_check;
+
 	mark_verifier_state_clean(env);
 
 	if (IS_ERR(btf_vmlinux)) {