futex: only access timeout on _WAIT ops
#106
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The `timeout` parameter is only used for `_WAIT` futex ops. For other ops, the `timeout` parameter is permitted to be an undefied value. The current implementation would then try to `copy_from_user` using the garbage pointer and fault, causing a missed wake-up and deadlock the calling process. Fix this by only accessing the timeout parmeter for `_WAIT` futex ops where the parameter's value must be valid.
arihant2math
approved these changes
Dec 29, 2025
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The
timeoutparameter is only used for_WAITfutex ops. For otherops, the
timeoutparameter is permitted to be an undefied value. Thecurrent implementation would then try to
copy_from_userusing thegarbage pointer and fault, causing a missed wake-up and deadlock the
calling process.
Fix this by only accessing the timeout parmeter for
_WAITfutex opswhere the parameter's value must be valid.