Merge branch 'btf-check-name'

Yonghong Song says:

====================
This patch set added name checking for PTR, ARRAY, VOLATILE, TYPEDEF,
CONST, RESTRICT, STRUCT, UNION, ENUM and FWD types. Such a strict
name checking makes BTF more sound in the kernel and future
BTF-to-header-file converesion ([1]) less fragile.

Patch #1 implemented btf_name_valid_identifier() for name checking
which will be used in Patch #2.
Patch #2 checked name validity for the above mentioned types.
Patch #3 fixed two existing test_btf unit tests exposed by the strict
name checking.
Patch #4 added additional test cases.

This patch set is against bpf tree.

Patch #1 has been implemented in bpf-next commit
Commit 2667a262 ("bpf: btf: Add BTF_KIND_FUNC
and BTF_KIND_FUNC_PROTO"), so there is no need to apply this
patch to bpf-next. In case this patch is applied to bpf-next,
there will be a minor conflict like
  diff --cc kernel/bpf/btf.c
  index a09b2f94ab25,93c233ab2db6..000000000000
  --- a/kernel/bpf/btf.c
  +++ b/kernel/bpf/btf.c
  @@@ -474,7 -451,7 +474,11 @@@ static bool btf_name_valid_identifier(c
          return !*src;
    }

  ++<<<<<<< HEAD
   +const char *btf_name_by_offset(const struct btf *btf, u32 offset)
  ++=======
  + static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
  ++>>>>>>> fa9566b0847d... bpf: btf: implement btf_name_valid_identifier()
    {
          if (!offset)
                  return "(anon)";
Just resolve the conflict by taking the "const char ..." line.

Patches #2, #3 and #4 can be applied to bpf-next without conflict.

[1]: http://vger.kernel.org/lpc-bpf2018.html#session-2
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -5,6 +5,7 @@
 #include <uapi/linux/types.h>
 #include <linux/seq_file.h>
 #include <linux/compiler.h>
+#include <linux/ctype.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/anon_inodes.h>
@@ -426,6 +427,30 @@ static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
 		offset < btf->hdr.str_len;
 }
 
+/* Only C-style identifier is permitted. This can be relaxed if
+ * necessary.
+ */
+static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
+{
+	/* offset must be valid */
+	const char *src = &btf->strings[offset];
+	const char *src_limit;
+
+	if (!isalpha(*src) && *src != '_')
+		return false;
+
+	/* set a limit on identifier length */
+	src_limit = src + KSYM_NAME_LEN;
+	src++;
+	while (*src && src < src_limit) {
+		if (!isalnum(*src) && *src != '_')
+			return false;
+		src++;
+	}
+
+	return !*src;
+}
+
 static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
 {
 	if (!offset)
@@ -1143,6 +1168,22 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	/* typedef type must have a valid name, and other ref types,
+	 * volatile, const, restrict, should have a null name.
+	 */
+	if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF) {
+		if (!t->name_off ||
+		    !btf_name_valid_identifier(env->btf, t->name_off)) {
+			btf_verifier_log_type(env, t, "Invalid name");
+			return -EINVAL;
+		}
+	} else {
+		if (t->name_off) {
+			btf_verifier_log_type(env, t, "Invalid name");
+			return -EINVAL;
+		}
+	}
+
 	btf_verifier_log_type(env, t, NULL);
 
 	return 0;
@@ -1300,6 +1341,13 @@ static s32 btf_fwd_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	/* fwd type must have a valid name */
+	if (!t->name_off ||
+	    !btf_name_valid_identifier(env->btf, t->name_off)) {
+		btf_verifier_log_type(env, t, "Invalid name");
+		return -EINVAL;
+	}
+
 	btf_verifier_log_type(env, t, NULL);
 
 	return 0;
@@ -1356,6 +1404,12 @@ static s32 btf_array_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	/* array type should not have a name */
+	if (t->name_off) {
+		btf_verifier_log_type(env, t, "Invalid name");
+		return -EINVAL;
+	}
+
 	if (btf_type_vlen(t)) {
 		btf_verifier_log_type(env, t, "vlen != 0");
 		return -EINVAL;
@@ -1532,6 +1586,13 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	/* struct type either no name or a valid one */
+	if (t->name_off &&
+	    !btf_name_valid_identifier(env->btf, t->name_off)) {
+		btf_verifier_log_type(env, t, "Invalid name");
+		return -EINVAL;
+	}
+
 	btf_verifier_log_type(env, t, NULL);
 
 	last_offset = 0;
@@ -1543,6 +1604,12 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
 			return -EINVAL;
 		}
 
+		/* struct member either no name or a valid one */
+		if (member->name_off &&
+		    !btf_name_valid_identifier(btf, member->name_off)) {
+			btf_verifier_log_member(env, t, member, "Invalid name");
+			return -EINVAL;
+		}
 		/* A member cannot be in type void */
 		if (!member->type || !BTF_TYPE_ID_VALID(member->type)) {
 			btf_verifier_log_member(env, t, member,
@@ -1730,6 +1797,13 @@ static s32 btf_enum_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	/* enum type either no name or a valid one */
+	if (t->name_off &&
+	    !btf_name_valid_identifier(env->btf, t->name_off)) {
+		btf_verifier_log_type(env, t, "Invalid name");
+		return -EINVAL;
+	}
+
 	btf_verifier_log_type(env, t, NULL);
 
 	for (i = 0; i < nr_enums; i++) {
@@ -1739,6 +1813,14 @@ static s32 btf_enum_check_meta(struct btf_verifier_env *env,
 			return -EINVAL;
 		}
 
+		/* enum member must have a valid name */
+		if (!enums[i].name_off ||
+		    !btf_name_valid_identifier(btf, enums[i].name_off)) {
+			btf_verifier_log_type(env, t, "Invalid name");
+			return -EINVAL;
+		}
+
+
 		btf_verifier_log(env, "\t%s val=%d\n",
 				 btf_name_by_offset(btf, enums[i].name_off),
 				 enums[i].val);