linux-kernel - Re: [PATCH -fixes v2] riscv: Fix out-of-bounds when accessing Andes per hart vendor extension array

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Message-ID: <20240814-overexert-baffling-1abf9a80c7b0@spud>
Date: Wed, 14 Aug 2024 23:26:30 +0100
From: Conor Dooley <conor@...nel.org>
To: Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Charlie Jenkins <charlie@...osinc.com>,
	Andy Chiu <andy.chiu@...ive.com>, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -fixes v2] riscv: Fix out-of-bounds when accessing Andes
 per hart vendor extension array

On Wed, Aug 14, 2024 at 09:26:19PM +0200, Alexandre Ghiti wrote:
> The out-of-bounds access is reported by UBSAN:
> 
> [    0.000000] UBSAN: array-index-out-of-bounds in ../arch/riscv/kernel/vendor_extensions.c:41:66
> [    0.000000] index -1 is out of range for type 'riscv_isavendorinfo [32]'
> [    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.11.0-rc2ubuntu-defconfig #2
> [    0.000000] Hardware name: riscv-virtio,qemu (DT)
> [    0.000000] Call Trace:
> [    0.000000] [<ffffffff94e078ba>] dump_backtrace+0x32/0x40
> [    0.000000] [<ffffffff95c83c1a>] show_stack+0x38/0x44
> [    0.000000] [<ffffffff95c94614>] dump_stack_lvl+0x70/0x9c
> [    0.000000] [<ffffffff95c94658>] dump_stack+0x18/0x20
> [    0.000000] [<ffffffff95c8bbb2>] ubsan_epilogue+0x10/0x46
> [    0.000000] [<ffffffff95485a82>] __ubsan_handle_out_of_bounds+0x94/0x9c
> [    0.000000] [<ffffffff94e09442>] __riscv_isa_vendor_extension_available+0x90/0x92
> [    0.000000] [<ffffffff94e043b6>] riscv_cpufeature_patch_func+0xc4/0x148
> [    0.000000] [<ffffffff94e035f8>] _apply_alternatives+0x42/0x50
> [    0.000000] [<ffffffff95e04196>] apply_boot_alternatives+0x3c/0x100
> [    0.000000] [<ffffffff95e05b52>] setup_arch+0x85a/0x8bc
> [    0.000000] [<ffffffff95e00ca0>] start_kernel+0xa4/0xfb6
> 
> The dereferencing using cpu should actually not happen, so remove it.
> 
> Fixes: 23c996fc2bc1 ("riscv: Extend cpufeature.c to detect vendor extensions")
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> ---

You're missing a changelog here, which is doubly important when you drop
tags provided to you on an earlier version.

>  arch/riscv/kernel/vendor_extensions.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/vendor_extensions.c b/arch/riscv/kernel/vendor_extensions.c
> index b6c1e7b5d34b..a8126d118341 100644
> --- a/arch/riscv/kernel/vendor_extensions.c
> +++ b/arch/riscv/kernel/vendor_extensions.c
> @@ -38,7 +38,7 @@ bool __riscv_isa_vendor_extension_available(int cpu, unsigned long vendor, unsig
>  	#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_ANDES
>  	case ANDES_VENDOR_ID:
>  		bmap = &riscv_isa_vendor_ext_list_andes.all_harts_isa_bitmap;
> -		cpu_bmap = &riscv_isa_vendor_ext_list_andes.per_hart_isa_bitmap[cpu];
> +		cpu_bmap = riscv_isa_vendor_ext_list_andes.per_hart_isa_bitmap;
>  		break;
>  	#endif
>  	default:
> -- 
> 2.39.2
> 
> 

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