Fix name lookup in PerformanceEntryReporter (use-after-free)#43646
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Fix name lookup in PerformanceEntryReporter (use-after-free)#43646tnovak wants to merge 1 commit into
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Summary: PerformanceEntryReporter maintains a buffer of RawPerformanceEntry objects, as well as a set of _pointers_ to elements within that buffer, used to find entries by name. However, those pointers aren't stable: BoundedConsumableBuffer internally uses a vector, and there are a few cases where existing references get invalidated: - When the vector's capacity changes (as new entries get inserted) [1] - After calling clear-with-predicate, which copies elements into a new vector This causes nameLookup to contain dangling pointers, and subsequent operations on it can result in use-after-free. Fix this by having BoundedConsumableBuffer reserve space for maxSize entries up front (which ensures that existing pointers remain valid after adding new elements) and by rebuilding nameLookup after clearing entries by name. Note that reserve() causes the buffer's memory use to be higher than before in case where the number of elements is small relative to the max size. Given the (only) existing usage in PerformanceEntryReporter, as well as the property that consumed elements remain in the buffer, that cost should be minor. Changelog: [Internal] [1] https://en.cppreference.com/w/cpp/container/vector/push_back Reviewed By: rshest Differential Revision: D55273403
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Summary:
PerformanceEntryReporter maintains a buffer of RawPerformanceEntry objects,
as well as a set of pointers to elements within that buffer, used to find
entries by name.
However, those pointers aren't stable: BoundedConsumableBuffer internally uses
a vector, and there are a few cases where existing references get invalidated:
This causes nameLookup to contain dangling pointers, and subsequent operations
on it can result in use-after-free.
Fix this by having BoundedConsumableBuffer reserve space for maxSize entries
up front (which ensures that existing pointers remain valid after adding new
elements) and by rebuilding nameLookup after clearing entries by name.
Note that reserve() causes the buffer's memory use to be higher than before in
case where the number of elements is small relative to the max size. Given the
(only) existing usage in PerformanceEntryReporter, as well as the property that
consumed elements remain in the buffer, that cost should be minor.
Changelog: [Internal]
[1] https://en.cppreference.com/w/cpp/container/vector/push_back
Reviewed By: rshest
Differential Revision: D55273403