[PATCH 2/2] powerpc/bpf: Reject atomic ops in ppc32 JIT

[Christophe Leroy]

Le 01/07/2021 à 17:08, Naveen N. Rao a écrit :
> Commit 91c960b0056672 ("bpf: Rename BPF_XADD and prepare to encode other
> atomics in .imm") converted BPF_XADD to BPF_ATOMIC and updated all JIT
> implementations to reject JIT'ing instructions with an immediate value
> different from BPF_ADD. However, ppc32 BPF JIT was implemented around
> the same time and didn't include the same change. Update the ppc32 JIT
> accordingly.
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>

Shouldn't it also include a Fixes tag and stable Cc as PPC32 eBPF was added in 5.13 ?

Fixes: 51c66ad849a7 ("powerpc/bpf: Implement extended BPF on PPC32")
Cc: stable at vger.kernel.org

> ---
>   arch/powerpc/net/bpf_jit_comp32.c | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
> index cbe5b399ed869d..91c990335a16c9 100644
> --- a/arch/powerpc/net/bpf_jit_comp32.c
> +++ b/arch/powerpc/net/bpf_jit_comp32.c
> @@ -773,9 +773,17 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   			break;
>   
>   		/*
> -		 * BPF_STX XADD (atomic_add)
> +		 * BPF_STX ATOMIC (atomic ops)
>   		 */
> -		case BPF_STX | BPF_XADD | BPF_W: /* *(u32 *)(dst + off) += src */
> +		case BPF_STX | BPF_ATOMIC | BPF_W:
> +			if (imm != BPF_ADD) {
> +				pr_err_ratelimited(
> +					"eBPF filter atomic op code %02x (@%d) unsupported\n", code, i);
> +				return -ENOTSUPP;
> +			}
> +
> +			/* *(u32 *)(dst + off) += src */
> +
>   			bpf_set_seen_register(ctx, tmp_reg);
>   			/* Get offset into TMP_REG */
>   			EMIT(PPC_RAW_LI(tmp_reg, off));
> @@ -789,7 +797,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   			PPC_BCC_SHORT(COND_NE, (ctx->idx - 3) * 4);
>   			break;
>   
> -		case BPF_STX | BPF_XADD | BPF_DW: /* *(u64 *)(dst + off) += src */
> +		case BPF_STX | BPF_ATOMIC | BPF_DW: /* *(u64 *)(dst + off) += src */
>   			return -EOPNOTSUPP;
>   
>   		/*
>