plist: fixed a few bugs (#2426)

* Fixed bug where plist()'s argument sentinel had incorrect type

* Fixed bug where if sentinel was different from zero, plist tried to dereference a null address

* Fixed bug where some error message in plist displayed 0x0x{address} due to incorrect formatting

* Added additional tests for plist's bugfixes

pwndbg/commands/plist.py

@@ -190,7 +190,7 @@ parser.add_argument(
 def plist(
     path: str,
     next: int,
-    sentinel: str,
+    sentinel: int,
     inner_name: str,
     field_name: str,
     offset: int,
@@ -395,7 +395,7 @@ def plist(
     for i, address in enumerate(addresses):
         if i < offset:
             continue
-        if address == sentinel:
+        if address in (0, sentinel):
             break
         try:
             # Always make sure we have the address of the outer structure.
@@ -416,7 +416,7 @@ def plist(
 
             print(f"{target_address:#x} {symbol}: {value}")
         except gdb.error as e:
-            print(message.error(f"Cannot dereference 0x{address:#x} for list link #{i + 1}: {e}"))
+            print(message.error(f"Cannot dereference {address:#x} for list link #{i + 1}: {e}"))
             print(message.error("Is the linked list corrupted or is the sentinel value wrong?"))
             return
 

tests/gdb-tests/tests/test_command_plist.py

@@ -65,6 +65,46 @@ def test_command_plist_dereference_limit_change_has_impact_on_plist(start_binary
     assert expected_out.match(result_str) is not None
 
 
+def test_command_plist_unreached_sentinel_does_not_cause_null_deference(start_binary):
+    """
+    Tests the plist command with a sentinel set to an address that is not reached does
+    not try to dereference zero
+    """
+    startup(start_binary)
+    expected_out = re.compile(
+        """\
+0[xX][0-9a-fA-F]+ <node_a>: 0\\s*
+0[xX][0-9a-fA-F]+ <node_b>: 1\\s*
+0[xX][0-9a-fA-F]+ <node_c>: 2\\s*
+0[xX][0-9a-fA-F]+ <node_d>: 3\\s*
+0[xX][0-9a-fA-F]+ <node_e>: 4\\s*
+\
+"""
+    )
+
+    result_str = gdb.execute("plist node_a next --sentinel 1 -f value", to_string=True)
+    assert expected_out.match(result_str) is not None
+
+
+def test_command_plist_invalid_address_deference_is_displayed_properly(start_binary):
+    """
+    Tests that the error message is displayed nicely when an incorrect address gets
+    deferenced
+    """
+    startup(start_binary)
+    gdb.execute("p node_a->next = 0x1234")
+    expected_out = re.compile(
+        """\
+0[xX][0-9a-fA-F]+ <node_a>: 0\\s*
+Cannot dereference 0x1234 for list link #2: Cannot access memory at address 0x1234\\s*
+Is the linked list corrupted or is the sentinel value wrong\\?\\s*
+\
+"""
+    )
+    result_str = gdb.execute("plist node_a next -f value", to_string=True)
+    assert expected_out.match(result_str) is not None
+
+
 def test_command_plist_flat_with_offset(start_binary):
     """
     Tests the plist for a non-nested linked list with an arbitrary offset value