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

[Chen-Yu Tsai]

On Fri, Dec 29, 2023 at 3:39 AM Stefan Wahren <wahrenst at gmx.net> wrote:
>
> 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 at gmx.net>

Reviewed-by: Chen-Yu Tsai <wens at csie.org>

> ---
> 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
>