Re: [PATCH] bpf: fix kmalloc bug in bpf_check

[Yonghong Song]

On 9/13/21 4:02 AM, Dongliang Mu wrote:
> Since 7661809d493b ("mm: don't allow oversized kvmalloc() calls
> ") does not allow oversized kvmalloc, it triggers a kmalloc bug warning
> at bpf_check.
>
> Fix it by adding a sanity check in th check_btf_line.
>
> Reported-by: syzbot+f3e749d4c662818ae439@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls")
> Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx>

Thanks for the fix. A similar patch has been proposed here:
https://lore.kernel.org/bpf/20210911005557.45518-1-cuibixuan@xxxxxxxxxx/

> ---
>   kernel/bpf/verifier.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 047ac4b4703b..3c5a79f78bc5 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9913,6 +9913,9 @@ static int check_btf_line(struct bpf_verifier_env *env,
>   	if (!nr_linfo)
>   		return 0;
>   
> +	if (nr_linfo > INT_MAX/sizeof(struct bpf_line_info))
> +		return -EINVAL;
> +
>   	rec_size = attr->line_info_rec_size;
>   	if (rec_size < MIN_BPF_LINEINFO_SIZE ||
>   	    rec_size > MAX_LINEINFO_REC_SIZE ||