Merge branch 'bpf-fix-incorrect-name-check-pass-logic-in-btf_name_valid_section'

Jeongjun Park says:

====================
bpf: fix incorrect name check pass logic in btf_name_valid_section

This patch was written to fix an issue where btf_name_valid_section() would
not properly check names with certain conditions and would throw an OOB vuln.
And selftest was added to verify this patch.
====================

Link: https://lore.kernel.org/r/20240831054525.364353-1-aha310510@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Alexei Starovoitov

kernel/bpf/btf.c

@@ -823,9 +823,11 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
 	const char *src = btf_str_by_offset(btf, offset);
 	const char *src_limit;
 
+	if (!*src)
+		return false;
+
 	/* set a limit on identifier length */
 	src_limit = src + KSYM_NAME_LEN;
-	src++;
 	while (*src && src < src_limit) {
 		if (!isprint(*src))
 			return false;

tools/testing/selftests/bpf/prog_tests/btf.c

@@ -3550,6 +3550,40 @@ static struct btf_raw_test raw_tests[] = {
 	},
 	BTF_STR_SEC("\0x\0?.foo bar:buz"),
 },
+{
+	.descr = "datasec: name with non-printable first char not is ok",
+	.raw_types = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* VAR x */                                     /* [2] */
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
+		BTF_VAR_STATIC,
+		/* DATASEC ?.data */                            /* [3] */
+		BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
+		BTF_VAR_SECINFO_ENC(2, 0, 4),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0x\0\7foo"),
+	.err_str = "Invalid name",
+	.btf_load_err = true,
+},
+{
+	.descr = "datasec: name '\\0' is not ok",
+	.raw_types = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* VAR x */                                     /* [2] */
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
+		BTF_VAR_STATIC,
+		/* DATASEC \0 */                                /* [3] */
+		BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
+		BTF_VAR_SECINFO_ENC(2, 0, 4),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0x\0"),
+	.err_str = "Invalid name",
+	.btf_load_err = true,
+},
 {
 	.descr = "type name '?foo' is not ok",
 	.raw_types = {