arm64: entry: Ensure branch through syscall table is bounded under speculation
Commit 6314d90e64
upstream.
In a similar manner to array_index_mask_nospec, this patch introduces an
assembly macro (mask_nospec64) which can be used to bound a value under
speculation. This macro is then used to ensure that the indirect branch
through the syscall table is bounded under speculation, with out-of-range
addresses speculating as calls to sys_io_setup (0).
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
parent
2e985d2647
commit
7a51d7d2f7
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@ -102,6 +102,17 @@
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hint #20
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hint #20
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.endm
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.endm
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/*
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* Sanitise a 64-bit bounded index wrt speculation, returning zero if out
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* of bounds.
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*/
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.macro mask_nospec64, idx, limit, tmp
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sub \tmp, \idx, \limit
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bic \tmp, \tmp, \idx
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and \idx, \idx, \tmp, asr #63
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csdb
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.endm
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/*
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/*
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* NOP sequence
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* NOP sequence
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*/
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*/
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@ -376,6 +376,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
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* x7 is reserved for the system call number in 32-bit mode.
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* x7 is reserved for the system call number in 32-bit mode.
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*/
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*/
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wsc_nr .req w25 // number of system calls
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wsc_nr .req w25 // number of system calls
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xsc_nr .req x25 // number of system calls (zero-extended)
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wscno .req w26 // syscall number
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wscno .req w26 // syscall number
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xscno .req x26 // syscall number (zero-extended)
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xscno .req x26 // syscall number (zero-extended)
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stbl .req x27 // syscall table pointer
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stbl .req x27 // syscall table pointer
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@ -884,6 +885,7 @@ el0_svc_naked: // compat entry point
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b.ne __sys_trace
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b.ne __sys_trace
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cmp wscno, wsc_nr // check upper syscall limit
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cmp wscno, wsc_nr // check upper syscall limit
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b.hs ni_sys
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b.hs ni_sys
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mask_nospec64 xscno, xsc_nr, x19 // enforce bounds for syscall number
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ldr x16, [stbl, xscno, lsl #3] // address in the syscall table
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ldr x16, [stbl, xscno, lsl #3] // address in the syscall table
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blr x16 // call sys_* routine
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blr x16 // call sys_* routine
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b ret_fast_syscall
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b ret_fast_syscall
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