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seccomp: reject x32 syscalls before evaluating policy rules - #284
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The x32 ABI shares AUDIT_ARCH_X86_64 with native x86_64, but sets bit 30 in syscall numbers. These numbers miss the native notification and deny checks and fall through to allow. Reject x32 syscalls at filter entry on x86_64, before argument rules can return. Place the architecture kill return next to its check so large filters cannot truncate the jump offset. Keep the syscall number reload after argument rules for native notification and deny checks. Add behavioral regressions for ABI rejection and native syscall actions, plus a child-process test that verifies SIGSYS without requiring x32 kernel support. All 1,765 workspace tests pass, with 8 doctests ignored. Fixes #282 Signed-off-by: Cong Wang <cwang@multikernel.io>
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x32 shares the x86_64 audit architecture but sets bit 30 in syscall numbers, allowing those requests to miss native notification and deny checks and fall through to allow.
Reject x32 syscalls before any policy rule can return. The guard is compiled only for x86_64. Move the shared architecture kill return next to its check to avoid jump-offset truncation in large filters, and preserve the syscall number reload after argument rules.
Regression tests cover native allow, deny, and notification behavior, rejection before an early allow, and large argument blocks. A child-process test verifies SIGSYS even when the kernel has x32 disabled.
Validation: full workspace suite passed on x86_64 with 1,765 tests passing and 8 doctests ignored. ARM64 and RISC-V hardware tests were not run.
Fixes #282