https://github.com/kovdan01 created
https://github.com/llvm/llvm-project/pull/82603
If `LLVM_TARGETS_TO_BUILD` does not contain `X86` and we try to run an x86
binary in lldb, we get a `nullptr` dereference in `LLVMDisasmInstruction(...)`.
We try to call `getDisAsm()` method on a `LLVMDisasmContext *DC` which is null.
The pointer is passed from
`x86AssemblyInspectionEngine::instruction_length(...)` and is originally
`m_disasm_context` member of `x86AssemblyInspectionEngine`. This should be
filled by `LLVMCreateDisasm(...)` in the class constructor, but not having X86
target enabled in llvm makes `TargetRegistry::lookupTarget(...)` call return
`nullptr`, which results in `m_disasm_context` initialized with `nullptr` as
well.
This patch adds if statements against `m_disasm_context` in
`x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(...)` and
`x86AssemblyInspectionEngine::FindFirstNonPrologueInstruction(...)` so
subsequent calls to `x86AssemblyInspectionEngine::instruction_length(...)` do
not cause a null pointer dereference.
>From 5c9ac5382958d88cbe2b89128957b3a0908c9d88 Mon Sep 17 00:00:00 2001
From: Daniil Kovalev <dkova...@accesssoftek.com>
Date: Thu, 22 Feb 2024 11:42:44 +0300
Subject: [PATCH] [lldb] Fix nullptr dereference on running x86 binary with
x86-disabled llvm
If `LLVM_TARGETS_TO_BUILD` does not contain `X86` and we try to run an
x86 binary in lldb, we get a `nullptr` dereference in
`LLVMDisasmInstruction(...)`. We try to call `getDisAsm()` method on a
`LLVMDisasmContext *DC` which is null. The pointer is passed from
`x86AssemblyInspectionEngine::instruction_length(...)` and is originally
`m_disasm_context` member of `x86AssemblyInspectionEngine`. This should
be filled by `LLVMCreateDisasm(...)` in the class constructor, but not having
X86 target enabled in llvm makes `TargetRegistry::lookupTarget(...)`
call return `nullptr`, which results in `m_disasm_context` initialized
with `nullptr` as well.
This patch adds if statements against `m_disasm_context` in
`x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(...)` and
`x86AssemblyInspectionEngine::FindFirstNonPrologueInstruction(...)` so
subsequent calls to `x86AssemblyInspectionEngine::instruction_length(...)` do
not cause a null pointer dereference.
---
.../UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp | 6 ++++++
1 file changed, 6 insertions(+)
diff --git
a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
index 2032c5a68d054c..6bfaa54135a959 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
@@ -909,6 +909,9 @@ bool
x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
if (!m_register_map_initialized)
return false;
+ if (m_disasm_context == nullptr)
+ return false;
+
addr_t current_func_text_offset = 0;
int current_sp_bytes_offset_from_fa = 0;
bool is_aligned = false;
@@ -1570,6 +1573,9 @@ bool
x86AssemblyInspectionEngine::FindFirstNonPrologueInstruction(
if (!m_register_map_initialized)
return false;
+ if (m_disasm_context == nullptr)
+ return false;
+
while (offset < size) {
int regno;
int insn_len;
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