subsys/llext: Fail if symbol name index is outside strings area

Avoid unintended out of bounds accesses.

Signed-off-by: Ederson de Souza <[email protected]>

Author: edersondisouza

subsys/llext/llext_load.c

@@ -542,6 +542,8 @@ static int llext_count_export_syms(struct llext_loader *ldr, struct llext *ext)
 	size_t ent_size = ldr->sects[LLEXT_MEM_SYMTAB].sh_entsize;
 	size_t syms_size = ldr->sects[LLEXT_MEM_SYMTAB].sh_size;
 	int sym_cnt = syms_size / sizeof(elf_sym_t);
+	elf_shdr_t *str_region = ldr->sects + LLEXT_MEM_STRTAB;
+	size_t str_reg_size = str_region->sh_size;
 	const char *name;
 	elf_sym_t sym;
 	int i, ret;
@@ -568,6 +570,12 @@ static int llext_count_export_syms(struct llext_loader *ldr, struct llext *ext)
 			return ret;
 		}
 
+		if (sym.st_name >= str_reg_size) {
+			LOG_ERR("Invalid symbol name index %d in symbol %d",
+				sym.st_name, i);
+			return -ENOEXEC;
+		}
+
 		uint32_t stt = ELF_ST_TYPE(sym.st_info);
 		uint32_t stb = ELF_ST_BIND(sym.st_info);
 		uint32_t sect = sym.st_shndx;