c18n: Improve detection of interrupted compartment #2220
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bsdjhb
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Sep 13, 2024
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Fix a bug where the dummy untrusted stack is not installed when a thread launches. Previously, the interrupted compartment is identified by checking whether its untrusted stack is a subset of the canonical copy of that stack. However, this subset relation should actually be inverted, that is, the untrusted stack of the interrupted compartment should be a superset of the canonical stack. Otherwise, a compartment which holds a portion of another compartment's stack would be able to impersonate it. (The SW_VMEM permission on the canonical stack has to be stripped before the comparison.) In addition, a bounds-check was missing for the tail-call scenario, which might result in reading from the stack table using an invalid index. Also, the tail-call scenario cannot be ruled-out even when the presumptive callee's stack is not allocated---we might be interrupted when a tail-call is taking place _and_ the callee's stack is unallocated.
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Previously, a bounds-check was missing for the tail-call scenario, which might result in reading from the stack table using an invalid index.
Also, the tail-call scenario cannot be ruled-out even when the presumptive callee's stack is not allocated---we might be interrupted when a tail-call is taking place and the callee's stack is unallocated.