Check if null buffer handed to SBProcess::ReadMemory

Add a check for a null destination buffer in SBProcess::ReadMemory,
and return an error if that happens.  If a Python SB API script
tries to allocate a huge amount of memory, the malloc done by the
intermediate layers will fail and will hand a null pointer to
ReadMemory.  lldb will eventually crash trying to write in to that
buffer.

Also add a test that tries to allocate an impossibly large amount
of memory, and hopefully should result in a failed malloc and hitting
this error codepath.

Differential Revision: https://reviews.llvm.org/D143012
rdar://104846609

1 files changed, 14 insertions, 0 deletions

diff --git a/lldb/test/API/python_api/process/TestProcessAPI.py b/lldb/test/API/python_api/process/TestProcessAPI.py
index cf05335b2384..36291fcc66b8 100644
--- a/lldb/test/API/python_api/process/TestProcessAPI.py
+++ b/lldb/test/API/python_api/process/TestProcessAPI.py
@@ -72,6 +72,20 @@ class ProcessAPITestCase(TestBase):
             exe=False,
             startstr=b'x')
 
+        # Try to read an impossibly large amount of memory; swig
+        # will try to malloc it and fail, we should get an error 
+        # result.
+        error = lldb.SBError()
+        content = process.ReadMemory(
+                val.AddressOf().GetValueAsUnsigned(), 
+                0xffffffffffffffe8, error)
+        if error.Success():
+            self.assertFalse(error.Success(), "SBProcessReadMemory claims to have "
+                      "successfully read 0xffffffffffffffe8 bytes")
+        if self.TraceOn():
+            print("Tried to read 0xffffffffffffffe8 bytes, got error message: ",
+                  error.GetCString())
+
         # Read (char *)my_char_ptr.
         val = frame.FindValue("my_char_ptr", lldb.eValueTypeVariableGlobal)
         self.DebugSBValue(val)