FUTEX_WAKE_OP: use atomic read-modify-write memory access#2147
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francescolavra wants to merge 2 commits intomasterfrom
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FUTEX_WAKE_OP: use atomic read-modify-write memory access#2147francescolavra wants to merge 2 commits intomasterfrom
francescolavra wants to merge 2 commits intomasterfrom
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March 15, 2026 19:58
In the op value extracted from the val3 argument is not a known value, Linux returns -ENOSYS.
In a FUTEX_WAKE_OP futex operation, the kernel modifies the memory pointed to by the 'uaddr2' argument; according to the Linux ABI, this modification must be done using atomic machine instructions.
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In a FUTEX_WAKE_OP futex operation, the kernel modifies the memory pointed to by the 'uaddr2' argument; according to the Linux ABI, this modification must be done using atomic machine instructions.
In addition, the syscall should return an error if the op value extracted from the val3 argument is not a known value.
Thanks to Niklas Femerstrand (@niklasfemerstrand) for reporting the race condition caused by non-atomic memory accesses.