Fix ResolverProxy use-after-free in HandleNodeBrowse #13291
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PR #13291: Size comparison from 99c1985 to 3ae2d08 Increases (13 builds for efr32, k32w, linux, p6, qpg, telink)
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HandleNodeBrowse decrements the ResolverProxy reference count, which will cause the object to be destructed if the counter reaches 0. It then increments the counter and accesses the object, which can be a use-after-free. This commit fixes the problem by ordering Release to occur after Retain. This commit also adds an abort to ReferenceCounted::Retain to check for cases like this when kInitRefCount is non-zero. For objects that are initialized with a non-zero reference count, we don't ever expect to call Retain when the count has already decremented to 0 because this indicates the object has been deleted. Fixes project-chip#13289
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PR #13291: Size comparison from 99c1985 to c50811c Increases (17 builds for efr32, esp32, linux, mbed, nrfconnect, p6, qpg, telink)
Full report (31 builds for efr32, esp32, k32w, linux, mbed, nrfconnect, p6, qpg, telink)
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) HandleNodeBrowse decrements the ResolverProxy reference count, which will cause the object to be destructed if the counter reaches 0. It then increments the counter and accesses the object, which can be a use-after-free. This commit fixes the problem by ordering Release to occur after Retain. This commit also adds an abort to ReferenceCounted::Retain to check for cases like this when kInitRefCount is non-zero. For objects that are initialized with a non-zero reference count, we don't ever expect to call Retain when the count has already decremented to 0 because this indicates the object has been deleted. Fixes project-chip#13289
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Problem
HandleNodeBrowse decrements the ResolverProxy reference count, which will cause the object to be destructed if the counter reaches 0. But then it increments the counter and accesses the object, which can be a use-after-free.
Fixes #13289
Change overview
This fixes the problem by ordering Release to occur after Retain. This also adds an abort to ReferenceCounted::Retain to check for cases like this when kInitRefCount is non-zero. For objects that are initialized with a non-zero reference count, we don't ever expect to call Retain when the count has already decremented to 0 because this indicates the object has been deleted.
Testing
Tested locally with a modified chip-tool that dynamically creates and initializes ResolverProxy objects for resolve calls, and calls their Shutdown method from within the OnNodeDiscoveryComplete callback. This reliably caused segfault without the fix and did not after. Additional instrumentation was added to log reference counts during testing and it was verified that these were now as expected.
The abort that has been added for ReferenceCounted::Retain should also provide significant coverage.