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Fix race when removing Cap_index (fix #163) 

Removing a Cap_index from Capability_map in core can happen twice, via
Cap_session_component or destructor of a Cap_mapping. That it's checked
whether the index is part of the map before removing it. This patch puts
the check into the remove method, so both operations are within the same
lock context, to remove a race condition.

This is a follow up fix for commit d287b9d893
This commit is contained in:
Stefan Kalkowski 2012-03-23 17:19:22 +01:00 committed by Norman Feske
parent c1e6657f49
commit 89db981280
2 changed files with 7 additions and 3 deletions
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8
base-foc/src/base/env/cap_map.cc vendored
View File

@ -89,8 +89,12 @@ void Genode::Capability_map::remove(Genode::Cap_index* i)
Lock_guard<Spin_lock> guard(_lock);
if (i) {
_tree.remove(i);
cap_idx_alloc()->free(i,1);
if (_tree.first())
i = _tree.first()->find_by_id(i->id());
if (i) {
_tree.remove(i);
cap_idx_alloc()->free(i,1);
}
}
}

2
base-foc/src/core/cap_session_component.cc
View File

@ -92,7 +92,7 @@ Cap_mapping::Cap_mapping(Core_cap_index* i, Native_thread_id r)
Cap_mapping::~Cap_mapping()
{
unmap();
cap_map()->remove(cap_map()->find(local->id()));
cap_map()->remove(local);
}