4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mark Rutland <mark.rutl...@arm.com>
From: Will Deacon <will.dea...@arm.com>
commit 6314d90e64936c584f300a52ef173603fb2461b5 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.rutl...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
[v4.9: use existing scno & sc_nr definitions]
Signed-off-by: Mark Rutland <mark.rutl...@arm.com> [v4.9 backport]
Tested-by: Greg Hackmann <ghackm...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/arm64/include/asm/assembler.h | 11 +++++++++++
arch/arm64/kernel/entry.S | 1 +
2 files changed, 12 insertions(+)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -94,6 +94,17 @@
.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
*/
.macro nops, num
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -795,6 +795,7 @@ el0_svc_naked: //
compat entry point
b.ne __sys_trace
cmp scno, sc_nr // check upper syscall limit
b.hs ni_sys
+ mask_nospec64 scno, sc_nr, x19 // enforce bounds for syscall number
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
blr x16 // call sys_* routine
b ret_fast_syscall
