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Commit ba17833f authored by Takaya Saeki's avatar Takaya Saeki
Browse files

libmodprobe: add missing locks in LoadWithAliases 

`Modprobe::LoadWithAliases` searches `module_loaded_` for a new element
without holding the lock of `module_loaded_lock_`. However,
`InsmodWithDeps` will insert an element later in this function, and
`LoadWithAliases` can be called by `LoadModulesParallel` in parallel.
Therefore `LoadWithAliases` touches `module_loaded_` while it's being
modified by other threads. That means it accesses corrputed memory.

This change inserts a necessary lock to fix this bug of
`LoadModulesParallel` and `LoadWithAliases`. This change does not
include changes to add thread safety annotations to prevent future same
problem, but following other changes will do that.

Bug: 400592897
Test: cuttlefish boots
Change-Id: Ib52a3b147cbe4122ae42c9fd377e9ea728a4aa41
parent 937d02a1

libmodprobe/libmodprobe.cpp

+16 −13
Original line number Diff line number Diff line
@@ -458,14 +458,16 @@ bool Modprobe::InsmodWithDeps(const std::string& module_name, const std::string& 


bool Modprobe::LoadWithAliases(const std::string& module_name, bool strict,

                               const std::string& parameters) {

    std::set<std::string> modules_to_load;

    bool module_loaded = false;

    {

        std::lock_guard guard(module_loaded_lock_);



        auto canonical_name = MakeCanonical(module_name);

        if (module_loaded_.count(canonical_name)) {

            return true;

        }



    std::set<std::string> modules_to_load = {canonical_name};

    bool module_loaded = false;



        modules_to_load.insert(std::move(canonical_name));

        // use aliases to expand list of modules to load (multiple modules

        // may alias themselves to the requested name)

        for (const auto& [alias, aliased_module] : module_aliases_) {
@@ -474,6 +476,7 @@ bool Modprobe::LoadWithAliases(const std::string& module_name, bool strict, 
            if (module_loaded_.count(MakeCanonical(aliased_module))) continue;

            modules_to_load.emplace(aliased_module);

        }

    }



    // attempt to load all modules aliased to this name

    for (const auto& module : modules_to_load) {