[jira] [Assigned] (MESOS-6424) Possible nullptr dereference in flag loading

["Benjamin Bannier (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MESOS-6424?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Benjamin Bannier reassigned MESOS-6424:
---------------------------------------

    Assignee: Benjamin Bannier

> Possible nullptr dereference in flag loading
> --------------------------------------------
>
>                 Key: MESOS-6424
>                 URL: https://issues.apache.org/jira/browse/MESOS-6424
>             Project: Mesos
>          Issue Type: Bug
>          Components: stout
>            Reporter: Benjamin Bannier
>            Assignee: Benjamin Bannier
>              Labels: coverity
>
> Coverity reports the following:
> {code}
> /3rdparty/stout/include/stout/flags/flags.hpp: 375 in flags::FlagsBase::add<mesos::internal::logger::rotate::Flags, std::basic_string<char, std::char_traits<char>, std::allocator<char>>, char [10], mesos::internal::logger::rotate::Flags::Flags()::[lambda(const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) (instance 1)]>(T2 T1::*, const flags::Name &, const Option<flags::Name> &, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, const T3 *, T4)::[lambda(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) (instance 1)]::operator ()(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) const()
> 369         Flags* flags = dynamic_cast<Flags*>(base);
> 370         if (base != nullptr) {
> 371           // NOTE: 'fetch' "retrieves" the value if necessary and then
> 372           // invokes 'parse'. See 'fetch' for more details.
> 373           Try<T1> t = fetch<T1>(value);
> 374           if (t.isSome()) {
>    CID 1374083:    (FORWARD_NULL)
>    Dereferencing null pointer "flags".
> 375             flags->*t1 = t.get();
> 376           } else {
> 377             return Error("Failed to load value '" + value + "': " + t.error());
> 378           }
> 379         }
> 380     
> ** CID 1374082:  Null pointer dereferences  (FORWARD_NULL)
> /3rdparty/stout/include/stout/flags/flags.hpp: 375 in flags::FlagsBase::add<mesos::internal::logger::LoggerFlags, Bytes, Megabytes, Option<Error> (*)(const Bytes &)>(T2 T1::*, const flags::Name &, Option<flags::Name>&, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, const T3 *, T4)::[lambda(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) (instance 1)]::operator ()(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) const()
> ________________________________________________________________________________________________________
> *** CID 1374082:  Null pointer dereferences  (FORWARD_NULL)
> /3rdparty/stout/include/stout/flags/flags.hpp: 375 in flags::FlagsBase::add<mesos::internal::logger::LoggerFlags, Bytes, Megabytes, Option<Error> (*)(const Bytes &)>(T2 T1::*, const flags::Name &, Option<flags::Name>&, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, const T3 *, T4)::[lambda(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) (instance 1)]::operator ()(flags::FlagsBase*, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&) const()
> 369         Flags* flags = dynamic_cast<Flags*>(base);
> 370         if (base != nullptr) {
> 371           // NOTE: 'fetch' "retrieves" the value if necessary and then
> 372           // invokes 'parse'. See 'fetch' for more details.
> 373           Try<T1> t = fetch<T1>(value);
> 374           if (t.isSome()) {
>    CID 1374082:  Null pointer dereferences  (FORWARD_NULL)
>    Dereferencing null pointer "flags".
> 375             flags->*t1 = t.get();
> 376           } else {
> 377             return Error("Failed to load value '" + value + "': " + t.error());
> 378           }
> 379         }
> 380     
> {code}
> The {{dynamic_cast}} is needed here if the derived {{Flags}} class got intentionally sliced (e.g., to a {{FlagsBase}}). Since the base class of the hierarchy ({{FlagsBase}}) stores the flags they would not be sliced away; the {{dynamic_cast}} here effectively filters out all flags still valid for the {{Flags}} used when the {{Flag}} was {{add}}'ed.
> It seems the intention here was to confirm that the {{dynamic_cast}} to {{Flags*}} succeeded like is done e.g., in {{flags.stringify}} and {{flags.validate}} just below.
> AFAICT this code has existed since 2013, but was only reported by coverity recently.



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