[PATCH] ACPICA: Fix operand resolution

[Amadeusz Sławiński]

In our tests we get UBSAN warning coming from ACPI parser. This is
caused by trying to resolve operands when there is none.

[    0.000000] Linux version 5.15.0-rc3chromeavsrel1.0.184+ (root@...) (gcc (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #1 SMP PREEMPT Sat Oct 16 00:08:27 UTC 2021
...
[ 14.719508] ================================================================================
[ 14.719551] UBSAN: array-index-out-of-bounds in /.../linux/drivers/acpi/acpica/dswexec.c:401:12
[ 14.719594] index -1 is out of range for type 'acpi_operand_object *[9]'
[ 14.719621] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc3chromeavsrel1.0.184+ #1
[ 14.719657] Hardware name: Intel Corp. Geminilake/GLK RVP2 LP4SD (07), BIOS GELKRVPA.X64.0214.B50.2009111159 09/11/2020
[ 14.719694] Call Trace:
[ 14.719712] dump_stack_lvl+0x38/0x49
[ 14.719749] dump_stack+0x10/0x12
[ 14.719775] ubsan_epilogue+0x9/0x45
[ 14.719801] __ubsan_handle_out_of_bounds.cold+0x44/0x49
[ 14.719835] acpi_ds_exec_end_op+0x1d7/0x6b5
[ 14.719870] acpi_ps_parse_loop+0x942/0xb34
...

Problem happens because WalkState->NumOperands is 0 and it is used when
trying to access into operands table. Actual code is:
WalkState->Operands [WalkState->NumOperands -1]
which causes out of bound access. Improve the check before above access
to check if ACPI opcode should have any arguments (operands) at all.

Link: https://github.com/acpica/acpica/pull/745
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@xxxxxxxxxxxxxxx>
Reviewed-by: Cezary Rojewski <cezary.rojewski@xxxxxxxxx>
---
 drivers/acpi/acpica/dswexec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpica/dswexec.c b/drivers/acpi/acpica/dswexec.c
index e8ad41387f84..489c9b9d8d15 100644
--- a/drivers/acpi/acpica/dswexec.c
+++ b/drivers/acpi/acpica/dswexec.c
@@ -389,9 +389,11 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
 
 		/*
 		 * All opcodes require operand resolution, with the only exceptions
-		 * being the object_type and size_of operators.
+		 * being the object_type and size_of operators as well as operands that
+		 * take no arguments.
 		 */
-		if (!(walk_state->op_info->flags & AML_NO_OPERAND_RESOLVE)) {
+		if (!(walk_state->op_info->flags & AML_NO_OPERAND_RESOLVE) &&
+		    (walk_state->op_info->flags & AML_HAS_ARGS)) {
 
 			/* Resolve all operands */
 
-- 
2.25.1