Fix: filter interpreter early-exits on uninitialized value

[deliverable/lttng-modules.git] / src / lttng-bytecode-interpreter.c

diff --git a/src/lttng-bytecode-interpreter.c b/src/lttng-bytecode-interpreter.c
index e183e330041a7d1e9883567477d41401c52b9566..153aeee656190330e34ce582b434b51a24883b99 100644 (file)
--- a/src/lttng-bytecode-interpreter.c
+++ b/src/lttng-bytecode-interpreter.c
@@ -20,7 +20,7 @@
  * to handle user-space read.
  */
 static
-char get_char(struct estack_entry *reg, size_t offset)
+char get_char(const struct estack_entry *reg, size_t offset)
 {
        if (unlikely(offset >= reg->u.s.seq_len))
                return '\0';
@@ -711,6 +711,39 @@ again:
        return LTTNG_INTERPRETER_RECORD_FLAG;
 }
 
+#ifdef DEBUG
+
+#define DBG_USER_STR_CUTOFF 32
+
+/*
+ * In debug mode, print user string (truncated, if necessary).
+ */
+static inline
+void dbg_load_ref_user_str_printk(const struct estack_entry *user_str_reg)
+{
+       size_t pos = 0;
+       char last_char;
+       char user_str[DBG_USER_STR_CUTOFF];
+
+       pagefault_disable();
+       do {
+               last_char = get_char(user_str_reg, pos);
+               user_str[pos] = last_char;
+               pos++;
+       } while (last_char != '\0' && pos < sizeof(user_str));
+       pagefault_enable();
+
+       user_str[sizeof(user_str) - 1] = '\0';
+       dbg_printk("load field ref user string: '%s%s'\n", user_str,
+               last_char != '\0' ? "[...]" : "");
+}
+#else
+static inline
+void dbg_load_ref_user_str_printk(const struct estack_entry *user_str_reg)
+{
+}
+#endif
+
 /*
  * Return 0 (discard), or raise the 0x1 flag (log event).
  * Currently, other flags are kept for future extensions and have no
@@ -1504,7 +1537,7 @@ uint64_t bytecode_interpret(void *interpreter_data,
                        estack_push(stack, top, ax, bx, ax_t, bx_t);
                        estack_ax(stack, top)->u.s.user_str =
                                *(const char * const *) &interpreter_stack_data[ref->offset];
-                       if (unlikely(!estack_ax(stack, top)->u.s.str)) {
+                       if (unlikely(!estack_ax(stack, top)->u.s.user_str)) {
                                dbg_printk("Bytecode warning: loading a NULL string.\n");
                                ret = -EINVAL;
                                goto end;
@@ -1514,7 +1547,7 @@ uint64_t bytecode_interpret(void *interpreter_data,
                                ESTACK_STRING_LITERAL_TYPE_NONE;
                        estack_ax(stack, top)->u.s.user = 1;
                        estack_ax(stack, top)->type = REG_STRING;
-                       dbg_printk("ref load string %s\n", estack_ax(stack, top)->u.s.str);
+                       dbg_load_ref_user_str_printk(estack_ax(stack, top));
                        next_pc += sizeof(struct load_op) + sizeof(struct field_ref);
                        PO;
                }
@@ -1532,7 +1565,7 @@ uint64_t bytecode_interpret(void *interpreter_data,
                        estack_ax(stack, top)->u.s.user_str =
                                *(const char **) (&interpreter_stack_data[ref->offset
                                                                + sizeof(unsigned long)]);
-                       if (unlikely(!estack_ax(stack, top)->u.s.str)) {
+                       if (unlikely(!estack_ax(stack, top)->u.s.user_str)) {
                                dbg_printk("Bytecode warning: loading a NULL sequence.\n");
                                ret = -EINVAL;
                                goto end;