libobs: Don't corrupt obs_properties in ..._remove_by_name #2257
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Xaymar
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The current implementation of obs_properties_remove_by_name corrupts the obs_properties_t object whenever it is called on the first or last property in the list. This leads to rapid unscheduled disassembly, and therefore must be fixed in order for this function to be used. Fixed by upstream PR obsproject/obs-studio#2257.
When obs_properties_remove_by_name is called on any obs_properties_t*, it corrupts the pointers for first_property and last which end up pointing at either unallocated memory or randomly into the heap memory. Neither of these is a good thing, and it usually leads to rapid unscheduled program behavior, also known as crashing and security issues. This fixes the issue by first checking if the pointer stored in props->last is identical to &cur->next, then checking if we are the only element (cur is also prev element), and if we are then the pointer is fixed to point back at props->first_property. Additionally fixes props->first_property which was never updated either.
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For the time being, StreamFX messes around with libOBS memory to prevent OBS Studio from crashing until this is merged. Since I don't know which version tag the next "stable" OBS Studio will have, I don't have it behind a conditional execution check yet. |
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Description
Fixes the corrupted obs_properties structure that happens when the obs_properties_remove_by_name encounters the first or the last element.
Motivation and Context
Stream Effects 0.8.0 makes heavy use of the obs_properties_remove_by_name feature, which breaks when used on the first or last element in the obs_properties_t*. This means that OBS enters an invalid state, and any future attempts to read from the obs_properties_t* object lead to memory corruption, or even a crash.
How Has This Been Tested?
Validated against new Stream Effects code. Stopped crashing.
Types of changes
Checklist: