Re: [PATCH bpf-next] bpf: fix bpf_dynptr_slice() to stop return an ERR_PTR.

[Martin KaFai Lau <martin.lau@linux.dev>]

On 8/3/23 4:12 PM, thinker.li@gmail.com wrote:
> From: Kui-Feng Lee <thinker.li@gmail.com>
> 
> Verify if the pointer obtained from bpf_xdp_pointer() is either an error or
> NULL before returning it.
> 
> The function bpf_dynptr_slice() mistakenly returned an ERR_PTR. Instead of
> solely checking for NULL, it should also verify if the pointer returned by
> bpf_xdp_pointer() is an error or NULL.
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/bpf/d1360219-85c3-4a03-9449-253ea905f9d1@moroto.mountain/
> Fixes: 66e3a13e7c2c ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr")
> Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
> ---
>   kernel/bpf/helpers.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 56ce5008aedd..eb91cae0612a 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -2270,7 +2270,7 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset
>   	case BPF_DYNPTR_TYPE_XDP:
>   	{
>   		void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);
> -		if (xdp_ptr)
> +		if (!IS_ERR_OR_NULL(xdp_ptr))

Considering the earlier bpf_dynptr_check_off_len() should have avoided the 
IS_ERR() case here, I think targeting bpf-next makes sense. Applied.