[5.3] Fix NULL deref for invalid mangled input (#31878) #31979
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The `Qo` operator expects to consume a type name and a list (terminated with a `y` empty list marker) from the stack. After popping the list, it doesn't check whether the stack is empty, so `$syQo` crashes (it pops down to the `y` then tries to pop again). This PR just adds the obvious check to guard against this. Resolves rdar://63128307
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airspeedswift
approved these changes
Jul 2, 2020
AnthonyLatsis
added
swift 5.3
🍒 release cherry pick
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This is a nomination to merge this change into release/5.3
Original description: The
Qooperator expects to consume a type name and a list (terminated with ayempty list marker) from the stack. After popping the list, it doesn't check whether the stack is empty, so$syQocrashes (it pops down to theythen tries to pop again).This PR just adds the obvious check to guard against this.
Risk: Minor. We just fail if a nullptr is encountered at one point where valid input should never give us a nullptr. The code would previously segfault at this point. This should only ever happen on malformed input.
Testing: Verified by original reporter, CI testing, local validation test runs.
Resolves rdar://63128307