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
|
@ -102,6 +102,17 @@
|
|||
hint #20
|
||||
.endm
|
||||
|
||||
/*
|
||||
* Sanitise a 64-bit bounded index wrt speculation, returning zero if out
|
||||
* of bounds.
|
||||
*/
|
||||
.macro mask_nospec64, idx, limit, tmp
|
||||
sub \tmp, \idx, \limit
|
||||
bic \tmp, \tmp, \idx
|
||||
and \idx, \idx, \tmp, asr #63
|
||||
csdb
|
||||
.endm
|
||||
|
||||
/*
|
||||
* NOP sequence
|
||||
*/
|
||||
|
|
|
@ -376,6 +376,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
|
|||
* x7 is reserved for the system call number in 32-bit mode.
|
||||
*/
|
||||
wsc_nr .req w25 // number of system calls
|
||||
xsc_nr .req x25 // number of system calls (zero-extended)
|
||||
wscno .req w26 // syscall number
|
||||
xscno .req x26 // syscall number (zero-extended)
|
||||
stbl .req x27 // syscall table pointer
|
||||
|
@ -884,6 +885,7 @@ el0_svc_naked: // compat entry point
|
|||
b.ne __sys_trace
|
||||
cmp wscno, wsc_nr // check upper syscall limit
|
||||
b.hs ni_sys
|
||||
mask_nospec64 xscno, xsc_nr, x19 // enforce bounds for syscall number
|
||||
ldr x16, [stbl, xscno, lsl #3] // address in the syscall table
|
||||
blr x16 // call sys_* routine
|
||||
b ret_fast_syscall
|
||||
|
|
Loading…
Reference in New Issue