[PATCH V2 1/2] ARM: sun9i: smp: Fix array-index-out-of-bounds read in sunxi_mc_smp_init

From: Stefan Wahren <wahrenst@gmx.net>
To: Chen-Yu Tsai <wens@csie.org>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Samuel Holland <samuel@sholland.org>
Cc: "Maxime Ripard" <mripard@kernel.org>,
	"Mylène Josserand" <mylene.josserand@bootlin.com>,
	linux-sunxi@lists.linux.dev, soc@kernel.org,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	linux-arm-kernel@lists.infradead.org,
	"Stefan Wahren" <wahrenst@gmx.net>
Subject: [PATCH V2 1/2] ARM: sun9i: smp: Fix array-index-out-of-bounds read in sunxi_mc_smp_init
Date: Thu, 28 Dec 2023 20:39:02 +0100	[thread overview]
Message-ID: <20231228193903.9078-1-wahrenst@gmx.net> (raw)

Running a multi-arch kernel (multi_v7_defconfig) on a Raspberry Pi 3B+
with enabled CONFIG_UBSAN triggers the following warning:

 UBSAN: array-index-out-of-bounds in arch/arm/mach-sunxi/mc_smp.c:810:29
 index 2 is out of range for type 'sunxi_mc_smp_data [2]'
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc6-00248-g5254c0cbc92d
 Hardware name: BCM2835
  unwind_backtrace from show_stack+0x10/0x14
  show_stack from dump_stack_lvl+0x40/0x4c
  dump_stack_lvl from ubsan_epilogue+0x8/0x34
  ubsan_epilogue from __ubsan_handle_out_of_bounds+0x78/0x80
  __ubsan_handle_out_of_bounds from sunxi_mc_smp_init+0xe4/0x4cc
  sunxi_mc_smp_init from do_one_initcall+0xa0/0x2fc
  do_one_initcall from kernel_init_freeable+0xf4/0x2f4
  kernel_init_freeable from kernel_init+0x18/0x158
  kernel_init from ret_from_fork+0x14/0x28

Since the enabled method couldn't match with any entry from
sunxi_mc_smp_data, the value of the index shouldn't be used right after
the loop. So move it after the check of ret in order to have a valid
index.

Fixes: 1631090e34f5 ("ARM: sun9i: smp: Add is_a83t field")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
---
Changes in V2:
- append another patch to fix return code check

 arch/arm/mach-sunxi/mc_smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-sunxi/mc_smp.c b/arch/arm/mach-sunxi/mc_smp.c
index cb63921232a6..6ec3445f3c72 100644
--- a/arch/arm/mach-sunxi/mc_smp.c
+++ b/arch/arm/mach-sunxi/mc_smp.c
@@ -807,12 +807,12 @@ static int __init sunxi_mc_smp_init(void)
 			break;
 	}

-	is_a83t = sunxi_mc_smp_data[i].is_a83t;
-
 	of_node_put(node);
 	if (ret)
 		return -ENODEV;

+	is_a83t = sunxi_mc_smp_data[i].is_a83t;
+
 	if (!sunxi_mc_smp_cpu_table_init())
 		return -EINVAL;

--
2.34.1

