Re: [PATCH] gdb: fix possible use-after-free when executing commands

[Jan Vrany <jan.vrany@labware.com>]

> > +  "  def invoke (self, arg, from_tty):" "" \
> > +  "    print (\"redefine_cmd output, msg = %s\" % self._msg)" "" \
> > +  "    self._msg = arg" "" \
> 
> Is it needed to assign arg to self._msg here?
> 

It is not, but found it usefull when testing the test.
This way, one may only comment the next line and test would
pass, without need to tweak following `gdb_test` lines.
Removed in new version (below)

> > +  "    redefine_cmd (arg)" "" \
> > +  "redefine_cmd (\"XXX\")" "" \
> > +  "end" ""
> > +
> > +gdb_test "redefine_cmd AAA" \
> > +  "redefine_cmd output, msg = XXX" \
> > +  "call command redefining itself 1"
> > +
> > +gdb_test "redefine_cmd BBB" \
> > +  "redefine_cmd output, msg = AAA" \
> > +  "call command redefining itself 2"
> > +
> 
> Note that in TCL code, we use an indent of 4 columns (and just like with
> C++ code, whole groups of 8 columns become a tab).
> 
> In order to isolate the new test from the other tests in the file, can
> you put the new test into its own `proc_with_prefix` function, and start
> with a fresh GDB?  That would mean calling clean_restart at the
> beginning of the proc.

Done, hopefully this is what you meant. Also I put the test to the end
of the file, as it is now in its own function.

-- >8 --
Subject: [PATCH v2] gdb/testsuite: add test for Python commands redefining
 itself

This commit adds a test that creates a Python command that redefines
itself during its execution. This is to test use-after-free in
execute_command ().

This test needs run with ASan enabled in order to fail when it
should.
---
 gdb/testsuite/gdb.python/py-cmd.exp | 30 +++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gdb/testsuite/gdb.python/py-cmd.exp b/gdb/testsuite/gdb.python/py-cmd.exp
index aa95a459f46..48c3e18f1cc 100644
--- a/gdb/testsuite/gdb.python/py-cmd.exp
+++ b/gdb/testsuite/gdb.python/py-cmd.exp
@@ -300,3 +300,33 @@ gdb_test_multiple "test_multiline" $test {
 	pass $test
     }
 }
+
+# Test command redefining itself
+
+proc_with_prefix test_command_redefining_itself {} {
+    # Start with a fresh gdb
+    clean_restart
+
+
+    gdb_test_multiline "input command redefining itself" \
+	"python" "" \
+	"class redefine_cmd (gdb.Command):" "" \
+	"  def __init__ (self, msg):" "" \
+	"    super (redefine_cmd, self).__init__ (\"redefine_cmd\", gdb.COMMAND_OBSCURE)" "" \
+	"    self._msg = msg" "" \
+	"  def invoke (self, arg, from_tty):" "" \
+	"    print (\"redefine_cmd output, msg = %s\" % self._msg)" "" \
+	"    redefine_cmd (arg)" "" \
+	"redefine_cmd (\"XXX\")" "" \
+	"end" ""
+
+    gdb_test "redefine_cmd AAA" \
+	"redefine_cmd output, msg = XXX" \
+	"call command redefining itself 1"
+
+    gdb_test "redefine_cmd BBB" \
+	"redefine_cmd output, msg = AAA" \
+	"call command redefining itself 2"
+}
+
+test_command_redefining_itself
-- 
2.35.1