On 09/17/2014 09:58 PM, Aaron Ballman wrote:
On Wed, Sep 17, 2014 at 4:04 AM, Vassil Vassilev
<[email protected]> wrote:
Hi,
I am attaching a patch addressing llvm.org/bugs/show_bug.cgi?id=20467
Vassil
Index: lib/Frontend/CompilerInstance.cpp
===================================================================
--- lib/Frontend/CompilerInstance.cpp (revision 217432)
+++ lib/Frontend/CompilerInstance.cpp (working copy)
@@ -339,6 +339,15 @@
if (!getHeaderSearchOpts().DisableModuleHash)
llvm::sys::path::append(SpecificModuleCache,
getInvocation().getModuleHash());
+
+ // If the path is not writable we can't do anything but diagnose.
+ if (llvm::sys::fs::exists(SpecificModuleCache.str()) &&
+ !llvm::sys::fs::can_write(SpecificModuleCache.str())) {
+ SourceLocation NoLoc;
+ PP->getDiagnostics().Report(NoLoc,
diag::err_module_cache_path_not_writable)
+ << SpecificModuleCache;
+ }
+
This has TOCTOU bugs -- the path could be writable at the point of
your check, but at the point which actually attempts to create a file
on that path can still fail. I think the correct way to handle this is
to handle the failure at the point of using the path, not attempting
to fail early.
Thanks! IIUC a good place to do this would be
clang::HeaderSearch::getModuleCachePath
<http://clang.llvm.org/doxygen/classclang_1_1HeaderSearch.html#a99ea51bfb4bb5f4742de10c8dfde0540>
? Would that be acceptable?
Vassil
~Aaron
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