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SubjectRe: [PATCH v2 bpf-next] bpf: Fix latent unsoundness in and/or/xor value tracking
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On 4/2/24 11:20 PM, Harishankar Vishwanathan wrote:
[...]
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index fcb62300f407..a7404a7d690f 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -13326,23 +13326,21 @@ static void scalar32_min_max_and(struct bpf_reg_state *dst_reg,
> return;
> }
>
> - /* We get our minimum from the var_off, since that's inherently
> + /* We get our minimum from the var32_off, since that's inherently
> * bitwise. Our maximum is the minimum of the operands' maxima.
> */
> dst_reg->u32_min_value = var32_off.value;
> dst_reg->u32_max_value = min(dst_reg->u32_max_value, umax_val);
> - if (dst_reg->s32_min_value < 0 || smin_val < 0) {

The smin_val is now unused, triggering the following warnings :

./kernel/bpf/verifier.c:13321:6: warning: unused variable 'smin_val' [-Wunused-variable]
13321 | s32 smin_val = src_reg->s32_min_value;
| ^~~~~~~~
./kernel/bpf/verifier.c:13352:6: warning: unused variable 'smin_val' [-Wunused-variable]
13352 | s64 smin_val = src_reg->smin_value;
| ^~~~~~~~
./kernel/bpf/verifier.c:13386:6: warning: unused variable 'smin_val' [-Wunused-variable]
13386 | s32 smin_val = src_reg->s32_min_value;
| ^~~~~~~~
./kernel/bpf/verifier.c:13417:6: warning: unused variable 'smin_val' [-Wunused-variable]
13417 | s64 smin_val = src_reg->smin_value;
| ^~~~~~~~
./kernel/bpf/verifier.c:13451:6: warning: unused variable 'smin_val' [-Wunused-variable]
13451 | s32 smin_val = src_reg->s32_min_value;
| ^~~~~~~~
./kernel/bpf/verifier.c:13479:6: warning: unused variable 'smin_val' [-Wunused-variable]
13479 | s64 smin_val = src_reg->smin_value;
| ^~~~~~~~

Removing these builds fine then, please follow-up with a v3.

Thanks,
Daniel

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