Merge branch 'bpf-core changes for preparation of HID-bpf'

Benjamin Tissoires says:

====================

Hi,

well, given that the HID changes haven't moved a lot in the past
revisions and that I am cc-ing a bunch of people, I have dropped them
while we focus on the last 2 requirements in bpf-core changes.

I'll submit a HID targeted series when we get these in tree, which
would make things a lore more independent.

For reference, the whole reasons for these 2 main changes are at
https://lore.kernel.org/bpf/20220902132938.2409206-1-benjamin.tissoires@redhat.com/

Compared to v10 (in addition of dropping the HID changes), I have
changed the selftests so we can test both light skeletons and libbbpf
calls.

Cheers,
Benjamin
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 52 insertions, 14 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 003f7ba19558..f3344a86d88d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2908,7 +2908,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 	return 0;
 }
 
-static int mark_chain_precision(struct bpf_verifier_env *env, int regno)
+int mark_chain_precision(struct bpf_verifier_env *env, int regno)
 {
 	return __mark_chain_precision(env, regno, -1);
 }
@@ -5233,6 +5233,25 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
 				env,
 				regno, reg->off, access_size,
 				zero_size_allowed, ACCESS_HELPER, meta);
+	case PTR_TO_CTX:
+		/* in case the function doesn't know how to access the context,
+		 * (because we are in a program of type SYSCALL for example), we
+		 * can not statically check its size.
+		 * Dynamically check it now.
+		 */
+		if (!env->ops->convert_ctx_access) {
+			enum bpf_access_type atype = meta && meta->raw_mode ? BPF_WRITE : BPF_READ;
+			int offset = access_size - 1;
+
+			/* Allow zero-byte read from PTR_TO_CTX */
+			if (access_size == 0)
+				return zero_size_allowed ? 0 : -EACCES;
+
+			return check_mem_access(env, env->insn_idx, regno, offset, BPF_B,
+						atype, -1, false);
+		}
+
+		fallthrough;
 	default: /* scalar_value or invalid ptr */
 		/* Allow zero-byte read from NULL, regardless of pointer type */
 		if (zero_size_allowed && access_size == 0 &&
@@ -6629,7 +6648,7 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	func_info_aux = env->prog->aux->func_info_aux;
 	if (func_info_aux)
 		is_global = func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_subprog_arg_match(env, subprog, caller->regs);
+	err = btf_check_subprog_call(env, subprog, caller->regs);
 	if (err == -EFAULT)
 		return err;
 	if (is_global) {
@@ -7576,6 +7595,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 {
 	const struct btf_type *t, *func, *func_proto, *ptr_type;
 	struct bpf_reg_state *regs = cur_regs(env);
+	struct bpf_kfunc_arg_meta meta = { 0 };
 	const char *func_name, *ptr_type_name;
 	u32 i, nargs, func_id, ptr_type_id;
 	int err, insn_idx = *insn_idx_p;
@@ -7610,8 +7630,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	acq = *kfunc_flags & KF_ACQUIRE;
 
+	meta.flags = *kfunc_flags;
+
 	/* Check the arguments */
-	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, *kfunc_flags);
+	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, &meta);
 	if (err < 0)
 		return err;
 	/* In case of release function, we get register number of refcounted
@@ -7632,7 +7654,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	/* Check return type */
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
-	if (acq && !btf_type_is_ptr(t)) {
+	if (acq && !btf_type_is_struct_ptr(desc_btf, t)) {
 		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
 		return -EINVAL;
 	}
@@ -7644,17 +7666,33 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		ptr_type = btf_type_skip_modifiers(desc_btf, t->type,
 						   &ptr_type_id);
 		if (!btf_type_is_struct(ptr_type)) {
-			ptr_type_name = btf_name_by_offset(desc_btf,
-							   ptr_type->name_off);
-			verbose(env, "kernel function %s returns pointer type %s %s is not supported\n",
-				func_name, btf_type_str(ptr_type),
-				ptr_type_name);
-			return -EINVAL;
+			if (!meta.r0_size) {
+				ptr_type_name = btf_name_by_offset(desc_btf,
+								   ptr_type->name_off);
+				verbose(env,
+					"kernel function %s returns pointer type %s %s is not supported\n",
+					func_name,
+					btf_type_str(ptr_type),
+					ptr_type_name);
+				return -EINVAL;
+			}
+
+			mark_reg_known_zero(env, regs, BPF_REG_0);
+			regs[BPF_REG_0].type = PTR_TO_MEM;
+			regs[BPF_REG_0].mem_size = meta.r0_size;
+
+			if (meta.r0_rdonly)
+				regs[BPF_REG_0].type |= MEM_RDONLY;
+
+			/* Ensures we don't access the memory after a release_reference() */
+			if (meta.ref_obj_id)
+				regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
+		} else {
+			mark_reg_known_zero(env, regs, BPF_REG_0);
+			regs[BPF_REG_0].btf = desc_btf;
+			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
+			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
-		mark_reg_known_zero(env, regs, BPF_REG_0);
-		regs[BPF_REG_0].btf = desc_btf;
-		regs[BPF_REG_0].type = PTR_TO_BTF_ID;
-		regs[BPF_REG_0].btf_id = ptr_type_id;
 		if (*kfunc_flags & KF_RET_NULL) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */